The Tomb of Balban (built c. 1287-1288 AD in Mehrauli, Delhi) is historically significant for being the earliest known building in India where the true arch (based on voussoirs) was successfully used for structural purposes. Earlier Sultanate buildings like the Quwwat-ul-Islam Mosque and Iltutmish's Tomb primarily relied on corbelling for arch-like openings, or their attempts at true arches failed (as seen in Iltutmish's Tomb).