Qutub Minar in Delhi, notable for its Indo-Islamic architecture, is 72 m (236 ft) high with 379 steps inside leading to the top. It is a tapering tower of five storeys, with a base diameter of 14.3 m (47 ft), which reduces to 2.75 m (9 ft) at the peak. Construction commenced in 1193 CE under Qutubuddin Aibak. His successor Shamsuddin Iltutmish added three storeys while the top storey was completed by Firuz Shah Tughlaq in 1386. The minaret, made of fluted red sandstone, is covered with carvings and verses from the Quran.