Alai Darwaza

The Mughal ruler Alauddin Khalji built up several things around the Qutab Minar in hopes to make it even grander than before--as if it wasn't grand enough to begin with.
One of the things he built is the Alai Darwaza--a main entrance for the mosque.

It's a perfect color contrast of red sandstone and white marble, and an excellent example of Islamic architecture from that time period.

It was meant to be a magnificent entrance to the mosque he enlarged, but most of his construction projects were not completed before he died.
Kinda sad that we don't use that entrance even now.