This building was built by Sultan Qutubuddin Aibak, but it took more than 20 years to complete, so it was completed under the then Sultan Iltutmish.

No wonder the building looks so strong. 20 years to complete a building isn't a child play, but was it funds that delay the building or materials. Anyway any building that is used for tourists purpose usually takes much time to be completed. It is a nice place to be indeed. Best of luck to you.