The Qutub Minar Complex is a historic district, with monuments from the Delhi Sultanate era dating back to the 12th century. It is one of the most popular tourist destinations in Delhi, India. Construction of the complex was begun by Qutb-ud-din Aibak, who later became the first Sultan of Delhi of the Mamluk dynasty. It was continued by his successor Iltutmish, and finally completed much later by Firoz Shah Tughlaq, in 1368 AD. Many subsequent rulers, including the Tughlaqs, Alauddin Khalji and the British added structures to the complex. Apart from the Qutub Minar and the Quwwat ul-Islam Mosque, other structures in the complex include the Alai Darwaza gate, the Alai Minar and the Iron pillar. Today, the adjoining area spread over with a host of old monuments, including Balban's Tomb, has been developed by the Archaeological Survey of India as the Mehrauli Archaeological Park, and INTACH has restored over forty monuments in the Park.