The Taj Mahal stands on the bank of River Yamuna, which otherwise serves as a wide moat defending the Great Red Fort of Agra, the center of the Mughal emperors until they moved their capital to Delhi in 1637. 
It was built by the fifth Mughal emperor, Shah Jahan in 1631 in memory of his second wife, Mumtaz Mahal, a Muslim Persian princess. 
The Taj rises on a high red sandstone base topped by a huge white marble terrace on which rests the famous dome flanked by four tapering minarets. Within the dome lies the jewel-inlaid cenotaph of the queen. 
So exquisite is the workmanship that the Taj has been described as "having been designed by giants and finished by jewellers". The only asymmetrical object in the Taj is the casket of the emperor which was built beside the queen’s as an afterthought. The emperor was deposed by his son and imprisoned in the Great Red Fort for eight years but was buried in the Taj. During his imprisonment, he had a view of the Taj. 
The dome is made of white marble, but the tomb is set against the plain across the river and it is this background that works its magic of colours that, through their reflection, change the view of the Taj. 
The colours change at different hours of the day and during different seasons. Like a jewel, the Taj sparkles in moonlight when the semi-precious stones inlaid into the white marble on the main mausoleum catch the glow of the moon.
The Taj is pinkish in the morning, milky white in the evening and golden when the moon shines.
photos courtesy: http://www.angelfire.com/in/myindia
Check this out- A true story of Tajmahal! http://www.hindunet.org/hindu_history/modern/taj_oak.html
For information on Agra: http://www.tajhub.com/
http://www.up-tourism.com/destination/agra/agra.htm, http:// www.agraonline.com/
