Ahmednagar Fort is one of the finest examples of late medieval military architecture in the Deccan, a massive round fortification ringed by a deep moat and studded with artillery bastions. It was built by Hussain Nizam Shah I in 1559, though the site had been fortified by Ahmad Nizam Shah, the kingdom's founder, before that. The fort survived multiple sieges, including a famous assault by the Mughal emperor Akbar in 1600.
The British found a more prosaic use for it: as a prison during the independence struggle, housing senior Congress leaders after the Quit India Movement of 1942. Nehru's cell is preserved with a small exhibit, and there is a Nehru museum inside the fort compound. The fort is maintained by the Indian Army, which means access to some sections is restricted, but the main historical areas including the ramparts and Nehru's cell are open to visitors.