SÓTANO DEL BARRO
Sótano del Barro is an enormous pit cave or sinkhole encircled by oak forests that serve as a refuge for the last remaining colony of military macaws in Central Mexico. It was formed 1.5 million years ago, when the bedrock collapsed, forming a cave whose mouth measures 420 by 200 meters and whose freefall drop equals 410 meters. A maximum depth is 455 meters.
The cave is located in one of the strict conservation zones of the Sierra Gorda Biosphere Reserve, and caving activities are not permitted since they can potentially be harmful to the threatened military macaws. The military macaws are threatened due to habitat destruction amongst other reasons.