Top 10 Largest Sinkholes

#1: Xiaozhai Tiankeng, Chongqing, China (≈2,170 ft deep; ≈2,000 ft long; ≈1,760 ft wide; volume >170 million cu ft)

Xiaozhai Tiankeng doesn’t look real until you lean over the rail and your inner ear says “absolutely not”: a two‑stage limestone chasm more than 2,100 feet deep, nearly 2,000 feet long, and 1,760 feet across, with a volume so huge clouds sometimes form inside. Locals call it “Heavenly Pit,” but it began as anything but divine—a subterranean river dissolved a gargantuan cave in Permian limestone until its roof collapsed twice, leaving a tiered void with a misty jungle on the first bench and a darker, primeval forest on the floor. The descent is a calf‑roasting 2,800‑step staircase hugging vertical walls streaked whiskey-brown with manganese varnish, past swallows spiraling in shafts of light and fern banks dripping from seeps; halfway down you catch the thunder of the underground Menglong River reappearing after miles of cave travel. Chinese speleologists mapped it with laser rangefinders in the 1990s, confirming world-record stats and nicknaming passages with pulp-novel flair: Dragon Door, Flying Waterfall Hall. Hidden gems include cave pearls the size of ping-pong balls, blind cavefish in sumps, and ancient coffins found wedged on ledges—a mystery likely tied to ethnic minority burial rites that favored dramatic perches. Statistics pile up like talus: top rim elevation about 4,600 feet, daily temperature swing on the floor a fraction of the rim’s thanks to cold-air pooling, annual rainfall amplified by how the pit funnels storms. Anecdotes: a villager once lowered a goat to test if spirits lived there (they didn’t, but the goat wasn’t thrilled); an early Western caver dropped a tape and waited six seconds for the clatter. Karst pros note this is a “tiankeng” (sky hole) on steroids—formed by underground void expansion, not just surface dissolution—and warn that its life story ends with slope failure slowly choking it with debris as the river undercuts new caverns elsewhere. On foggy mornings the pit exhales like some vegetated volcano; at night, bats exit in dark rivers, and if you kill your headlamp you can hear water dripping a hundred feet away. Stand on that railing and you learn a metric no chart lists: heartbeats per minute when 1,000 feet of nothing is under your boots.

#2: Dashiwei Tiankeng, Guangxi, China (≈1,000 ft deep; ≈2,000 ft across; rim elevation ≈2,800 ft)

Dashiwei looks like a meteor strike wrapped in jungle—an almost perfectly round chasm roughly 2,000 feet wide and about 1,000 feet deep, its walls jungled with cycads and figs that cling to hairline cracks in Devonian limestone. It formed in a cluster: the Leye–Fengshan Geopark hosts more than two dozen tiankengs, but Dashiwei is king, with a floor big enough for a soccer stadium ringed by a circular cliff where waterfalls vanish into swallow holes audible but invisible. The entry trail winds through bamboo to an observation deck that hovers over void; those with caver permits descend via rope into darkness that smells of wet rock and guano, discovering stalagmites as thick as trucks and phreatic tubes polished like marble from a vanished underground river. Legends say dragons coiled here; 1950s villagers eyeing bat guano for fertilizer tossed ropes and found only bruised pride. Stats sharpen the imagery: vertical walls in some sectors overhang 30 feet; humidity in the pit hovers near 100%; biodiversity surveys logged 80+ fern species in one expedition. Hidden gems include troglobitic shrimp in rim pools fed by mist; bird nests so high biologists needed drones; and a “stone waterfall” of flowstone drapery 150 feet tall, frozen in mid-cascade. Engineers drool at the acoustics—shout and you get echoes back like a chorus—and at the microclimate: cool air pooling makes mornings fog-dense, afternoons a steam bath. In 2004, a Chinese–British team rigged the first full bottom-to-rim rope ascend, a 1,000-foot jug made hellish by mud-caked ascenders and leeches; one climber described the pit’s soundscape as “rain that never reaches you.” Geologically, Dashiwei is a snapshot of limestone dissolution fed by monsoon rain, thick vegetation acids, and structural joints that guided water like blueprints—once void size crossed a threshold, snap, the roof dropped. Eventually, more roofs will go; new tiankengs seed in the dark while this one slowly fills with soil, seeds, and the occasional unlucky goat. For now, though, it’s a perfect circle of vertigo that turns knees to gelatin and makes every drone pilot’s footage look like CGI.

#3: El Zacatón, Tamaulipas, Mexico (depth ≈1,099 ft water column; surface diameter ≈360 ft; water temp ≈86°F)

El Zacatón is a sinkhole you don’t see until you’re on top of it—a round, reed-fringed pool 360 feet across whose surface looks like dark jade glass until a breeze pushes floating zacate (grass) mats into slow spins. Peer down and it goes black: a 1,099‑foot flooded shaft, the deepest known water‑filled sinkhole in the world, warm (mid‑80s °F) thanks to hydrothermal input, riser of sulfur bubbles that smell like bad eggs on windless days. NASA liked it so much they sent a robot—DEPTHX—in 2007 to test autonomous navigation for Europa’s ocean, mapping the shaft and finding side caverns big enough to swallow houses. The limestone here is part of the Sierra de Tamaulipas karst, riddled with cenote-like features called “pozas”; El Zacatón is the queen, fed from below by CO₂-rich water that keeps it stratified and possibly anoxic at depth—meaning rational divers fear it and irrational ones become legends. In 1993, Jim Bowden and Sheck Exley attempted to break records here; Exley died at 879 feet, an event etched soberly into cave-diving lore; Bowden surfaced with the bends and trauma, swearing never again. Stats: visibility often <10 feet because of suspended sulfur bacteria; pH slightly acidic; walls coated in microbial mats that give off an earthy, sweet smell in hot months. Hidden gems: a side pool, Poza Azufrosa, bubbles like a witch’s cauldron; aboveground ruins of a 19th‑century hacienda show locals used zacate mats as rafts to cross; legends say a hairless cow was dragged under by a demon—more likely a vent sucked it down. Geologically, sulfuric acid speleogenesis likely helped: H₂S from deeper fluids oxidized to sulfuric acid, dissolving limestone from below and creating a vertical tube later intersected by surface collapse. In the evening, bats skim insects over the mirror; mornings, steam wisps in cool air; year-round, you feel watched by water you can’t see into. El Zacatón is proof that the deepest voids aren’t always dry—and that the bravest explorers sometimes come in stainless-steel hulls, not wetsuits.

#4: Sima Humboldt, Bolívar, Venezuela (depth ≈1,030 ft from rim; mouth diameter ≈1,150 ft; floor “island” ≈1,000 ft across)

Perched atop the quartz-sandstone tabletop of Sarisariñama tepui, Sima Humboldt drops 1,000 feet through rock 1.5–2.0 billion years old—a perfect circular mouth 1,150 feet wide opening into a cylinder so vast the floor holds its own isolated forest. The sinkhole’s origin story reads like sci‑fi: in 1961, a bush pilot reported a “dark crater” on the tepui; Venezuelan scientists first rappelled in 1974, naming this shaft and its neighbor Sima Martel after two explorers. Inside, bromeliads grow as trees, fungus gnats swarm in clouds, and frogs call that exist nowhere else—evolution trapped by stone. The floor is not central beneath the rim; an “island” of older rock stands within a moatlike depression, suggesting collapse in stages and an enigmatic subsurface structure. Stats: walls overhang in places; rim elevation ~4,500 ft; humidity near 100%; rain often falls inside even when the tepui top is sunny as clouds form from evaporated floor moisture that hits cool air. Hidden gems: cave beetles with reduced eyes, quartz sand dunes on ledges where wind funnels, and petroglyph-like manganese streaks that look intentional. Anecdotes: first descent teams carried everything—food, rope, toilet paper—back out at 1,000‑foot jug-ups, describing hallucinations in the green gloom; one scientist called it “botanically insane.” Geologists argue whether piping (subsurface erosion of sand by groundwater) or chemical dissolution in quartzitic rock (rare but possible) made the void; most settle on a combo of solution along fractures and mechanical cave-in, aided by relentless rainfall. No tourist trail here: permits are rare, helicopters scar the ecology, and a misstep means a freefall into a Jurassic lost world. Sima Humboldt is tall in another way too—its walls record eons of weathering lines, like tree rings in stone, each shade a wetter or drier epoch. Stand on the rim at dawn and you’ll feel vertigo from the tilt of the wind alone.

#5: Crveno Jezero (Red Lake), Imotski, Croatia (rim-to-water depth ≈1,740 ft; lake depth ≈1,000 ft; rim diameter ≈1,600 ft)

Red Lake is an oxymoron: an open-air abyss filled with blue water named for red. The “red” comes from iron-oxide-stained Cretaceous limestone walls plunging an estimated 1,740 feet from rim to lake surface, making it one of the deepest sinkholes on Earth; the lake itself runs another ~1,000 feet down, for a total void of almost half a mile if you follow the shaft into submerged caverns divers have barely touched. Standing at the guardrail near Imotski, you peer into a vertical lagoon framed by sheer cliffs pocked with caves where bats swirl at dusk; on windy days, ripples look tiny as raindrops from 1,700 feet up. Stats: rim elevation ~1,640 feet above sea level; lake level fluctuates 30–60 feet seasonally; divers mapped submerged tunnels in 2017, finding a 1,148‑foot depth before equipment said “enough.” Hidden gems: an endemic cave shrimp, Troglocaris anophthalmus, washed into the lake during floods; karst windows nearby feeding Blue Lake (Modro Jezero), which drains periodically and once hosted a soccer match on its dried bed. Anecdotes: local legend says a giant named Gavan cursed by saints created the hole; modern legend: in 2014 two Slovenians BASE-jumped into the lake, paddled to shore, and free-climbed out—because Croatians apparently needed more reasons to shake heads. Geologically, the sinkhole likely formed by collapse over a massive cave chamber; red staining hints at long-term oxidation of iron-rich layers, while the circular shape implies collapse centered over a columnar void. Winter sees ice rims; summer brings dragonflies and tourists with selfie sticks carefully leaning out. In late afternoon, a phenomenon locals call “the sun kiss” happens when the last ray hits the lake surface, a dot of light at the bottom of darkness—a daily spectacle that makes 1,740 feet feel intimate. It’s tall inverted: a skyscraper of missing rock lined with iron lipstick.

#6: Sótano de las Golondrinas, San Luis Potosí, Mexico (depth ≈1,220 ft to debris; freefall ≈1,090 ft; mouth 205 ft × 110 ft)

Sótano de las Golondrinas—“Cave of Swallows”—is a vertical statement: a 1,220‑foot pit, its first 1,090 feet a clean freefall, mouth just 205 by 110 feet, widening to a 500‑foot chamber where limestone walls are streaked like tiger fur from water flow. At dawn, millions of white-collared swifts and green parakeets shoot out in a spiral tornado, insects exploding before beaks; evening, they dive back in at 60 mph, using echolocation clicks like micro-bats. For cavers, it’s Mecca: a rappel that takes 10–20 minutes depending on rope and guts, a jug that can take two hours; for BASE jumpers, it was fantasy until jumps were banned after too many near misses with birds and walls. Stats: temperature at bottom ~77°F; humidity high; floor littered with centuries of guano, occasionally igniting in rare spontaneous combustion when dry chunks oxidize fast. Hidden gems: bioluminescent fungi glowing on fallen logs; a small side chamber where you can hear the stream that carved it still dripping in a rhythm older than the Aztecs. Anecdotes: legend says a girl lowered to retrieve a goat never returned; modern reality: a researcher once had a rope sheath melt from friction and lived to preach “don’t rappel fast.” Geologically, Golondrinas formed along a joint in Lower Cretaceous limestone, water widening it until the roof went; now chemical dissolution continues on walls, widening the shaft a millimeter at a time. The local Huastec people respect it as sacred; tourists pay small fees to ejido members who manage access, guiding sometimes barefoot on mud-slick ledges with grace. Sunrise there is religion: a black funnel of birds uncoiling into a pink sky—your cue that sometimes the most thrilling part of a 1,200‑foot pit happens in the top 200 feet.

#7: Dragon Hole (Sansha Yongle Blue Hole), Paracel Islands, South China Sea (depth ≈987 ft; mouth diameter ≈426 ft; near-vertical walls)

Called Longdong by Chinese fishermen, Dragon Hole is the ocean’s deepest known blue hole—a nearly circular sapphire portal 426 feet across at the surface, plunging 987 feet through carbonate bedrock and ancient reef until sensors hit silt and anoxia. Unlike Bahamas or Belize holes connected to caves, Dragon Hole is an isolated shaft in a coral platform, stratified like a parfait: clear, oxygenated surface water on top, then a hydrogen sulfide “stink layer,” then dead zone. The hole made headlines in 2016 when Chinese scientists dropped a CTD to 987 feet and found 20+ layers of chemoclines, plus life clinging to transitions—shrimp, worms, and cyanobacteria communities making do without sunlight. Stats: salinity shifts with storms; internal tides pulse; rim slopes from reefs that still host groupers and sharks. Hidden gems: legends tie it to Journey to the West’s Monkey King palace; fishermen swear lost anchors descend forever; researchers spot plastic bags at 500 feet, a modern talisman of reach. Diving is limited—tech divers could, but permissions are thorny, currents tricky, and the toxic layer can fry lungs if you surface wrong. Geologically, blue holes like this often form when sea level was lower, karst pits on exposed platforms later drowned; Dragon Hole might be a collapsed cave, or a doline that intersected reef voids, now acting as a chemical reactor in the South China Sea. Storms glass the surface; on calm days it’s an eye staring back at sky; drop a pebble and you see rings at 400 feet turn cobalt. Dragon Hole is tall in negative space, a vertical oceanic cave that proves not all sinkholes breathe air.

#8: Dean’s Blue Hole, Long Island, Bahamas (depth ≈663 ft; mouth diameter ≈330 ft surface, widening to ≈100 ft)

Dean’s Blue Hole is deceptive: from shore it looks like a big, placid pool; swim 20 yards and the sandy bottom vanishes into midnight. At 663 feet deep, it’s the world’s second-deepest known seawater blue hole and a free-diver’s cathedral—William Trubridge set multiple world records here, descending on a single breath to depths that make chest cavities pancake. The hole’s circular at the surface (about 330 feet), then funnels to a narrow throat before ballooning into a cavern ~100 feet across, its walls draped in calcite and life perched at light’s limit. Stats: water temp mid‑80s °F; visibility superb until storms stir; thermoclines slight; haloclines minimal as it connects to the sea via submerged tunnels. Hidden gems: a pillar of stalactites deep inside proving the cave formed in air during Pleistocene low stands; a resident school of tarpon circling divers like curious ghosts; phosphorescent plankton that ignite night swimmers in neon traceries. Anecdotes: a 2013 freediving tragedy took Nicholas Mevoli’s life here, sparking safety debates; locals tell of goats once dumped to test “no monsters.” Geologically, Dean’s formed by karst dissolution of limestone, then partial collapse; later, sea flooded in, turning the void into a blue sink window to the aquifer. At noon, sunbeams spear the throat like cathedral light; at dusk, nurse sharks cruise the rim while kids cannonball oblivious to abyss. Dean’s teaches scale: 663 feet is two Statues of Liberty plus change—a void you measure in lung capacity, not ladders.

#9: Great Blue Hole, Lighthouse Reef, Belize (diameter ≈1,000 ft; depth ≈410 ft; rim depth ≈35 ft)

Seen from the air, the Great Blue Hole looks photoshopped—an ink drop in turquoise, a near-perfect 1,000‑foot circle over a 410‑foot shaft drilled into Pleistocene limestone. Jacques Cousteau anchored the Calypso here in 1971, declaring it one of the world’s top dives after blasting a route through stalactites the size of barrels; today, dive boats tie off at moorings, drop you to 130 feet for a stalactite glimpse, then haul you up before nitrogen says hello. Stats: thermocline around 50–60 feet; hammerheads sometimes ghost by in winter; dissolved oxygen plummets below 300 feet, life sparse in the deeper, hydrogen-sulfide-laced layers. Hidden gems: stalactite “chandeliers” prove the cave formed in air ~153,000–15,000 years ago when sea level was 300–400 feet lower; dive at slack tide and Caribbean reef sharks orbit calmly; snorkelers spot midnight parrotfish mowing algae right over the abyss. Anecdotes: a 2018 submersible expedition livestreamed dead conches and trash at 350 feet, a bummer epilogue; early divers used Navy tables and steel tanks, surfacing woozy; local fishermen used it as a weather mark—waves break differently over the void. Geologically, it’s a classic carbonate platform doline later flooded, widened by solution and collapse; a coral rim now rings it, alive and bleached in patches, witness to warming seas. From above, you see color as depth code: pale sand, aquamarine shallows, midnight in a heartbeat. Tourists fly drones; frigatebirds ride thermals; and somewhere a turtle crosses that lip never guessing how far down dark goes.

#10: Guatemala City Sinkhole (Zona 2, 2010 event) (depth ≈300 ft; width ≈100 ft; near-vertical walls)

Not all giants are ancient: in May 2010, buildings in Guatemala City’s Zona 2 vanished—swallowed by a 100‑foot-wide, 300‑foot-deep near-perfect cylinder that locals dubbed a “sinkhole” but engineers call a “piping feature.” Volcanic ash and pumice under the city—unlithified, like talcum—had been Swiss-cheesed by leaky sewer lines and torrential downpours from Tropical Storm Agatha; water surged, soil liquefied, and gravity did the rest, sucking a factory, intersection, and three-story building into a vertical shaft whose walls looked machined. Photos went viral: a round, black maw in urban fabric, eerie in its cleanliness. Stats: depth to water table ~330 feet; surrounding soils cohesionless; rainfall that week >3 inches in 24 hours; prior sinkholes (2007) hinted at the risk. Hidden gems: none—just rebar, couches, streetlamps at the bottom, grim evidence that karst isn’t required for collapse. Anecdotes: a security guard survived by clinging to rubble; residents reported “a roaring sound like a jet” seconds before pavement disappeared; conspiracy theories blamed secret tunnels. Geologically, this isn’t limestone dissolution but suffosion: water excavated fine ash into sewers, voids grew until a thin “roof” collapsed, revealing a shaft following pipe routes. The city filled it with cement and gravel, rerouted lines, but smaller holes keep appearing—proof that human plumbing can carve faster than rainacid. From the rim (fenced now), you smelled damp dust, not sulfur; saw darkness, not stalactites; felt urban anxiety, not wilderness awe. Still, by pure geometry it’s one of the largest sudden collapses recorded in a city, a modern reminder that “sinkhole” can be an infrastructure grade, not just a geology term.

The planet’s biggest sinkholes are negative cathedrals—physics problems you can walk into, chemistry labs you can dive, and cautionary tales you can pave over. They form by limestone dissolving, sulfuric acid eating rock from below, tectonic faults gaping, lava tubes caving, or pipes leaking under asphalt. Their metrics—2,100 feet of air, 1,099 feet of warm water, 1,000 feet of blue ocean hole—anchor our sense of scale, but the real depth lies in what they hold: endemic blind shrimp, billion-year quartz gardens, lost goats, freedivers chasing silence, and city blocks swallowed in a gulp. Each is temporary—talus piles rise, roofs thin, rims erode—so visit gently: respect sacred sites, dive with brains attached, don’t toss rocks for echo thrills. Look down and you’re peering into time—layers of collapse frozen mid-fall. Look up from the bottom and the sky is a round, distant coin. Either way, sinkholes remind us the ground is only a suggestion, and emptiness can be the most impressive architecture of all.