From the Wikipedia entry on the Taj Mahal:
Soon after Taj Mahal’s completion, Shah Jahan was deposed and put under house arrest at nearby Agra Fort by his son Aurangzeb. Legend has it that he spent the remainder of his days gazing at the Taj Mahal. Upon Shah Jahan’s death, Aurangzeb buried him in the Taj Mahal next to his wife. By late 19th century, parts of Taj Mahal had fallen badly into disrepair. During the time of Indian rebellion of 1857, Taj Mahal faced defacement by British soldiers and government officials, who chiseled out precious stones and lapis lazuli from its walls. At the end of 19th century British viceroy Lord Curzon ordered a massive restoration project, completed in 1908. He also commissioned the large lamp in interior chamber, modelled based on one in a Cairo mosque. It was during this time the garden was remodelled with British looking lawns that are visible today.
On the repairs: “If I had never done anything else in India, I have written my name here, and the letters are a living joy.”