Actun Tunichil Muknal, the Maya archaeological cave, is in Belize.
Often shortened to ATM, Actun Tunichil Muknal means “Cave of the Stone Sepulchre” and lies in Belize’s Cayo District, near San Ignacio. The cave is within the Tapir Mountain Nature Reserve and contains a river passage, chambers and extensive mineral formations.
Maya groups used the cave for ritual activity. Archaeologists have found human remains, ceramics and stone objects, including vessels marked with “kill holes”—deliberate perforations associated with releasing a vessel’s spiritual contents. Several remains became coated with calcite from the cave environment.
The best-known find is the Crystal Maiden, a calcite-encrusted skeleton believed to belong to a teenager and often interpreted as evidence of sacrifice, though details of the individual’s death remain uncertain. Because the site is fragile and archaeologically important, access is controlled through licensed tour operators. It is sometimes confused with other Maya cave sites in Mexico or Guatemala, but ATM is in Belize.