Cave of Swallows

Interesting facts

A person falling from the mouth without a parachute would take almost ten seconds to reach the floor.

Each evening, about once a minute, a group of perhaps fifty swifts peels off the circling flock and dives straight down into the shaft.

The opening measures about 49 by 62 metres, but the shaft bells out below to roughly 303 by 135 metres at the floor.

Depending on which side of the lip you measure from, the drop is about 333 metres of freefall or 370 metres.

The local Huastec people have known the cave since ancient times; cavers were first shown it on 27 December 1966.

The first documented descent to the floor was made on 4 April 1967.

Rappelling to the bottom can take up to an hour, while climbing out may take more than two hours.

The shaft formed in limestone of Middle Cretaceous age, and its floor is covered with a thick layer of debris and bird guano.

Why it is worth it

Despite the name, no swallows live in the Cave of Swallows. The birds that made it famous are white-collared swifts and green parakeets, thousands of them, nesting on ledges inside a single limestone shaft that drops roughly 370 meters — deep enough, cavers point out, to swallow most skyscrapers whole with room left above.

Twice a day the cave puts on a show that predates any tourism: at dawn the birds spiral up and out of the pit to feed, and at dusk they spiral back down and disappear into the walls, thousands of separate flight paths resolving into one visible column of motion. Cavers and BASE jumpers who use the site have agreed among themselves to avoid the rim at those hours and to rig only one fixed rope point year-round, so the colony isn't disturbed by traffic.

The freefall itself is short and the way out is not: a BASE jumper reaches the floor in well under fifteen seconds, but climbing or being hauled back to the rim takes anywhere from forty minutes to two hours — part of why the site draws committed jumpers rather than casual thrill-seekers.

Good to know

Depth: about 370 meters to the floor, the largest single cave shaft in the world and the second-deepest pit in Mexico.
Access for descent and BASE jumping is restricted to one designated rim point, agreed among cavers to protect the bird colony.

Best time to visit

Early morning or the hour before sunset, when the swifts and parakeets fly in or out in their spiraling columns.

Getting there

45 km from Ciudad Valles. General Francisco Javier Mina International Airport (TAM) is about 149 km away.

From the encyclopaedia

The Cave of Swallows, also called the Cave of the Swallows, is an open-air pit cave in the municipality of Aquismón, San Luis Potosí, Mexico. The elliptical mouth, on a slope of karst, is 49 by 62 m wide and is undercut around all of its perimeter, widening to a room approximately 303 by 135 m wide. The floor of the cave is a 333 m (1,093 ft) freefall drop from the lowest side of the opening, with a 370 m (1,210 ft) drop from the highest side, making it the largest known cave shaft in the world, the second deepest pit in Mexico and perhaps the 11th deepest sheer drop in the world.

Wikipedia · CC BY-SA 4.0