Located at the highest point of the Old Fort in Delhi known as Purana Qil'a, Sher Mandal may have been built by Mughal emperor Humayun as an astronomical library and pleasure tower during his rule in Delhi between 1530 and 1556, which was interrupted for fifteen years by the Afghan Suri Dynasty. Some historians attribute it to Suri ruler Sher Shah Sur (reg. 1540-1545) based on vague references to the building in his biography Tarikh-i-Sher Shahi, commissioned by Mughal emperor Akbar in 1579. There is no epigraphical evidence to support either claim. In any case, Sher Mandal along with Qila-i-Kuhna Masjid, is one of two surviving structures within the fort ramparts from the mid sixteenth century.
The building is a two story octagonal structure crowned with a pillared and domed pavilion (chattri). Built entirely of local red sandstone, both stories are punctuated with deeply recessed arched niches on each side of the octagon. While the niches on the second story are connected to form a verandah around a central chamber, those on the lower story only allow for entry arches into the tower. The upper chamber is cruciform in plan and opens into a verandah through four doors. Continuous eaves (chajja) runs below the roof parapet.
Sources:
Asher, Catherine B. The New Cambridge History of India: Architecture of Mughal India. Cambridge: Cambridge University Press, 1992. 32-33.
Koch, Ebba. Mughal Architecture: An Outline of its History and Development (1526-1858). Munich: Verlag, 1991. 37-39.
Nath, R. History of the Sultanate Architecture. New Delhi: Abhinav Publications, 1978. 89-90.