From The Hindu:
Whose is the mystery grave next to the one of Razia Sultan? Various conjectures have been made by historians and visitors. According to Gaynor Barton who, along with another Englishwoman, Laurraine Malone, wrote a book, “Old-Delhi-Ten Easy Walks”, Razia was murdered by robbers while resting under a tree in presumably present-day Haryana. Dr Ishwari Prasad, the noted historian, however states that it was not robbers but some villagers who killed her and her lover, Altunia, probably to find favour with her jealous siblings. How did she then come to be buried behind the tomb of Hazrat Turkman Bayabani? Who brought her body there and what happened to the body of Altunia?
Razia was known not as Sultana but as Sultan because in those days the orthodox courtiers of her father would not have willingly followed one who manifested her womanhood in an all-male preserve. She gave no quarter to her enemies, including her brothers, Ruknuddin, debauchee among them. Like Antony, making his oration at Caesar’s funeral and inciting the Romans against the conspirators of the great conqueror, Razia, dressed in the robes of a mystic, addressed the citizens of Delhi, asking them to avenge the death of her slain younger brother, Muizuddin. The mob did just what it was supposed to do and Razia ascended the throne. But her reign of three years was short and tragic, even though she turned her defeat at the hands of the powerful Governor of Lahore into a personal victory by winning his hand, just as she had earlier gained the support of the Abyssinian master of the stable, Yaqut. But both she and the Turkish Altunia were defeated and later put to death by a hostile mob in 1240 AD. That in brief is the history of the woman who lies under a shabby tomb. Few people in the neighbourhood know its relevance, though there is a grave in Karnal also said to be hers.