Purana Qila -
The Purana Qila was raised over the ancient mound, which is traditionally associated with Indraprastha, the city of Mahabharata story. Sher Shah Suri (A.D. 1540-45) demolished the city of Dinpanah built by Humayun and on the same site raised this citadel. It is irregular oblong on plan with bastions on corners and three gates, opening on the north, south and west. It is believed that Sher Shah left Purana Qila incomplete and Humayun completed it. Excavation at Purana Qila has yielded the evidence of a
continuous habitation from pre-Mauryan times, through Sunga, Saka-Kushan period (1100 B.C.-A.D.
300), Gupta (circa A.D. 400-600), post-Gupta (circa A.D. 700-800), Rajput (A.D. 1206-1526) to early
Mughal period (A.D. 1526-1556). Amongst small finds of the different periods, notable are a gold-plated Gupta coin, inscribed sealings, coins of Samantadeva and of some Delhi Sultans and Chinese porcelain fragment bearing an inscription of the Ming period (A.D. 1465-87). Among structural remains exposed may be mentioned a hammam of the Mughal period.
Sher Mandal: It is a double-storeyed octagonal tower of red sandstone relieved by marble, surmounted by
an octagonal pavilion or chhatri. On the second storey, the central chamber is cruciform, with recesses on its four sides. Purpose of the building is not certain, but was probably used by Humayun as his library, from the step of which he fell down as he knelt in response to the Muazzin's call for prayer and ultimately died.
Qal'a-i-Kuhna Masjid: It was built by Sher Shah in A.D. 1541. Its prayer hall is rectangular, pierced by five horse-shoe shaped arches in the front. The central arch, higher than the others and framed within projection, is flanked by narrow fluted pilasters. This mosque occupies an important position in the development of the Mughal mosque architecture.