Qutub Minar is a brick tower that was built around 1200 AD by the first Muslim ruler of Delhi to commemorate a military victory. Probably because it is so easily accessible, it is the most visited historical site in India.
In Peru, we saw lots of churches that were built on top of Inca foundations. So much so that there are few pure Inca buildings left (this is what makes Machu Picchu so unique: it was hidden in the jungle and the Spaniards never found it). The Muslim invaders of India couldn't destroy and build over all the Hindu temples of course -- there were too many of them -- but they seem have to given it their best shot. This hallway around the Qutub complex consists of pillars ransacked from Hindu and Jain temples.