Agra Fort is a monument, about 2.5 km northwest of the Taj Mahal. A royal residence of Mughals for generations, the fort was used to be the site of a battle during the Indian rebellion of 1857. The fort has a semicircular plan; its chord lies parallel to the river while its walls are seventy feet high. Double ramparts have massive circular bastions at intervals, with battlements, embrasures and string courses. Four gates were provided on its four sides.