Cenotes are natural sinkholes or pits that connect the surface to an underground body of water. Often these locations were once underground lakes or sea caves but have had a portion of their roof collapse, exposing the water-filled chamber to the surface. Fictional cenotes may have roots or vines that hang down from their openings and waterfalls may cascade from the surface to their depths. Often they connect to vast underground cavern systems or to underground rivers. They may be used as wells or as locations for human sacrifice. They may contain treasure chests. Cenotes may be beast pits, piranha pools, leviathan territories, or dens to other creatures.