If you go down to the forests of Mexico today (or any day, really), be sure to watch where you step. The municipality of Aquismón, in San Luis Potosí is home to the Cave of Swallows, an open air shaft that descends 370 metres from the forest floor.
The largest pit cave in the world, it’s almost deep enough to house Melbourne’s Eureka Tower, and could easily accommodate the entirety of Sydney’s Citigroup Centre. Which is all a very Australian-centric way of saying: this is a huge cave.
The local Huastec people had long known about what the Spanish call the Sótano de las Golondrinas, but it was only visited by white people in 1966. Since then it’s become a beacon for vertical cavers, who rappel down over the course of a full hour. During this time the rope can get so hot due to friction that water has to be sprayed to keep it from breaking.
Base-jumpers have a much quicker time of it: it takes only 10 seconds to reach the waters below if you simply fling yourself off – and nearly three hours to get back up. If you’d like to know what that looks like (the base-jumping, not the climbing back out), check out this short video narrated by Sir David Attenborough.
Via Atlas Obscura