Management of water systems is often considered by anthropologists and archaeologists as a catalytic force in the rise of prehistoric, highly developed societies. Recent studies of the hydraulic engineering skills of the ancient lowland Maya have shown some of their remarkable capbilities for controlling water, including the construction of stone dams. This paper examines new evidence of one such Maya construction located in western Belize, Central America, and discusses the size, form, probable age, and function of tbis feature.