West Baray near Angkor Thom

The pond is the largest manmade reservoir of the ancient Khmers. When we took a boat on it, it felt like travelling in a lake. This lake was man made a thousand years ago.
Just consider the dimensions:
West Baray is eight kilometres in length and two kilometres in width.
It originally covered an area of 1760 hectares and had an average depth of 7 meters, holding 123 million cubic litres of water.
Built in the 11th Century, started by King Suryavarman I (reigned 1001-1050) and completed by King Udayadityavarman II (reigned 1050-1066)