Purana Qila

Lonely Planet review

With massive walls and three gateways, Purana Qila was the site of ancient Indraprastha. The Afghan ruler, Sher Shah, who briefly interrupted Mughal sovereignty by defeating Humayun, completed the fort during his reign (1538-45), before Humayun regained control of India.

Entering from the south gate you'll see the small, octagonal, red-sandstone tower, the Sher Mandal, later used by Humayun as a library. It was while descending the stairs of this tower in 1556 that he slipped and sustained injuries from which he later died. Just beyond it is the Qila-i-Kuhran Mosque, or Mosque of Sher Shah. There's a small archaeological museum (admission free) just inside the main gate.