Sher Mandal
The Sher Mandal stands to the south of the mosque. This double-storeyed octagonal tower of red sandstone with steep stairs leading up to the roof. The structure was intended to be higher than its existing height but the work was stopped due to the untimely death of Sher Shah. It was built by Sher Shah and was used as a library by Humayun after he recaptured the fort. It is also one of the first observatories of delhi. The first being in Pir Gharib at Hindu Rao at Ridge built in 14th century by Firoz shah Tughlaq.The tower is topped by an octagonal chhatri supported by eight pillars and decorated with white marble. Inside there are remnants of the decorative plaster-work and traces of stone-shelving where, presumably, the emperor's books were placed. This was also the tragic spot where, on 24 January 1556 Humayun slipped while on his way to the evening namaz, fell headlong down the stairs and died of his injuries two days later.
Nai ka Kot Ruins
South of Tughlaqabad and once connected to it by a causeay is the fortress of Adilabad, which was built by Muhammad-bin-Tughlaq. In plan it is a smaller version of Tughlaqabad, with the trademark sloping walls of huge stone. Inside Adilabad was the legendary Qasr-i-hazaar satun or the Palace of a thousand pillars, which seems to have been a really popular idea back then (see Bijai Mandal). The palace had a huge audience hall, which was built on columns of varnished wood. Towards the southern gateway you can still see a vaulted corridor which used to be flanked by guardrooms. Adilabad has all the marks of a fine Tughlaq building with that style's typically austere walls, bare surfaces, corbeled arches and crenellation.