Taj Mahal is a UNESCO World Heritage Site located in Agra, Uttar Pradesh. It is considered as one of the seven new wonders of the world. It was built by the fifth Muslim Mogul emperor, Shah Jahan out of marble. Shah Jahan built the monument in the honour of his late wife, Mumtaz Mahal.
More details of Taj Mahal can be obtained at https://en.wikipedia.org/wiki/Taj_Mahal
The Govt. of Uttar Pradesh runs the official website http://www.tajmahal.gov.in. This website provides useful information about the history of Taj Mahal, including Frequently Asked Questions at http://www.tajmahal.gov.in/faq_taj.html. This provides useful information on the visiting hours, costs and key contacts for tourists seeking information.