Qutb Minar (Urdu: قطب مینار), also spelled Qutub or Qutab, is the tallest minar (73 metres) in India originally an ancient Islamic Monument, inscribed with Arabic inscriptions, and is a UNESCO World Heritage Site. Located in Delhi, the Qutb Minar is made of red sandstone and marble. The stairs of the tower has 379 steps, is 72.5 metres (237.8 ft) high, and has a base diameter of 14.3 metres, which narrows to 2.7 metres at the top. Construction was started in 1192 by Qutb-ud-din Aibak and was carried on by his successor, Iltutmish. In 1368, Firoz Shah Tughlak constructed the fifth and the last storey. It is surrounded by several other ancient and medieval structures and ruins, collectively known as the Qutb complex.