The western end of Cuba is riddled with caves including the largest of all, the Great Cavern of Santo Tomas. This immense cave, with more than 44 km of passages, is in the Sierra de Quemados, part of the Sierra de los Organos in he Guaniguanico range.

The cave entrance leads into a maze of six levels with more than fifty separate caves. One of these the Escaralata Cavern, is filled with a fine crystalline formation made up of calcium-containing minerals. The Santa Tomas River and its tributary, El Penate, flow through the lower levels.