The fort is said to be constructed on the historic site of Indraprastha (900BC) by Humayun and Sher Shah. Covering a circuit of about a mile, the walls of the fort have three gates and are surrounded by a mat fed by the river Yamuna. The wall was built by Humayun while the buildings in the fort are attributed to Sher Shar. The notable buildings that have survived in the fort are the Sher Mandal and the Quila-I-kholina Mosque.

Sher Mandal is a two storeyed octagonal tower which was used by Humayun as his library. The mosque, built around 1541-42, is a landmark in Indo Islamic architecture. The architect has shown skill by enriching each part with moulding, bracketed openings, marble inlay, carving and other establishments. A variety of materials have also been used to construct the small mosque (168 x 44 feet). The entrance arch is of marble, the spandrels of red sandstone studded with marble bossed, the columns and pilasters of black and white marble.