For 350 years, the Taj Mahal in Agra has reigned luminous and splendid as perhaps the most admired monument in the world. Visitors who gazed across the Yamuna River from the Taj pavilions have viewed what appears to be little more than farmers' fields and barren ground. But historical references as well as paintings from the time of Shahjahan (r. 1628-58) reveal that it was once densely covered by rectangular walled enclosures and lush vegetation...