in the book "asarus sanadid", syed ahmed khan writes that this mausoleum houses the tomb of fahim khan. khan was an attendant of abdul rahim khan-i-khana and died in 1626, during the reign of mughal emperor jahangir. s.a.a. naqvi of the archaeological survey of india opines that this building was built even before the humayun's tomb. his conjecture is based on the fact that the enclosure wall of the humayun's tomb contains a gateway to this building. also the enclosure wall contains recessed arches which are absent in the nila gumbad.