din Mahmud , eldest son of Iltumish . First true dome, Alai Darwaza , Qutb complex , Delhi , built in 1311 CE, by first Khilji Sultan of Delhi, Ala-ud-din Khilji . First true arch, Balban's tomb , Mehrauli Archeological Park, Delhi , built c. 1287 CE, by Ghiyas ud din