Ajatshatru Fort, Rajgir, Bihar

Built by Ajatshatru (6th century B.C.), the king of Magadha during the Buddha's time. The 6.5 sq.meter Ajatshatru's Stupa is also believed to have been built by him in Rajgir.

According to historical sources King Ajatshatru (6th Century BC), after becoming the king, kept his father Bimbisara in a small prison (Bimbisara’s Prison) inside his fort (Fort of Ajatshatru). Built in the 6th Century BC, there were stone towers on all four corners of this 60 Meter long & 2 Meter broad square wall. King Bimbisara chose this place in the last years of his life so that he can see Lord Buddha going to Gridh Koot Parvat every morning. Lord Buddha resided there in this period.Now, at this place, ruins of the walls of the fort, path of the chariots & remains of the bath are visible. Ajatshatru’s Stupa (6.5 Meter) is also situated here. Many archaeological remains have been found here in excavation, which include small rooms of stone............
http://famousindiantouristplaces.blogspot.com