Left to right: Terry, Carl, and Andreas about to leave for Mexico.

Andreas's Honda Accord loaded up for a caving trip to Mexico.

The back of Lane's van after transferring all of our caving gear.

Driving through Matamoros.

On the highway south of Matamoros.

Approaching a dangerous curve.

Our guide and David hiking to El Sótano del Barro.

A succulent plant growing by the edge of the pit.

A succulent plant growing on a rock.

Left to right: Andreas, Carl, and our guide feeding the rope into the pit.

Andreas feeding the rope into the pit using his rappell rack.

Andreas beginning the rappel into El Sótano.

Wide-angle view of the entrance.

Carl at the bottom of El Sótano.

Terry almost at the end of his rappel.

Looking across El Sótano while climbing the rope.

Looking down to the bottom of El Sótano during a rest in the climb.

Carl clearing the lip at the top of the ascent.

Left to right: David, Carl, and Andreas hauling the 460-meter rope out of El Sótano.

Left to right: Andreas, our guide, and David loading roaps onto a burro for the trip down the mountain.

The wild staircases at the entrance to Los Pozas.

David at the top of the entrance tower staircase.

Left to right: Lane and David walking carefully along the entranceway staircase.

Lane ascending a concrete staircase.

Lane coming across a bridge in the jungle.

Left to right: Andreas, David, and Lane sitting by a fountain.

A concrete tower rising out of the jungle.

A wall of concrete arches at Los Pozas.

A wrought-iron door along a pathway.

The entrance to Los Pozas under the flying stairway.

A waterfall downstream from Los Pozas.

Carl feeding the rope into Sótano de Tlamaya.

Carl about to rappel into the entrance pit of Sótano de Tlamaya.

Left to right: Carl and David rigging one of the drops in Tlamaya.

Lane at the top of one of the climbs.

Left to right: Carl and Terry carrying the 460-meter rope in two backpacks for some night-time rigging.

A caver rappelling the 333-meter drop into Sótano de las Golondrinas.

David at the bottom of Sótano de las Golondrinas.

Andreas on knots at the top of the 333-meter climb.

David after his second climb that day.

Looking across the entrance of Golondrinas as Carl completes his climb.