Manila, is located on the eastern shores of Manila Bay. The Pasig River bisects the city in the middle. Almost all of the city sits on top of centuries of prehistoric alluvial deposits built by the waters of the Pasig River and on some land reclaimed from Manila Bay. The city's land has been altered substantially by human intervention, with considerable land reclamation along the waterfronts since the American colonial times. Some of the natural variations in topography have been evened out due to the urbanization of the city. Manila lies 800 miles (1,300 km) from mainland Asia.