Around 700 AD, Tikal had the largest dam built by the ancient Maya of Central America, used sand filtration to cleanse water entering reservoirs, a "switching station" that accommodated seasonal filling and release of water, and the deepest, rock-cut canal segment in the Maya lowlands. All this to support a population at Tikal of perhaps 60,000 to 80,000 inhabitants and an estimated population of five million in the overall Maya lowlands.