Originally conceived as a nature walk, it was transformed secretly into plans for a shopping mall.

The whole project crashed soon after it began amid allegations of wrongdoing and corruption.

Sandstone rubble remains strewn across the dump site.

RK Dixit, the ASI’s senior official at the Taj, has an office inside the edifice of the Great Gate. He sits under a white domed roof, with a swirling symbol of the sun at its apex. The room has one window, shaded by a honeycomb screen of red sandstone, which offers a direct view of the mausoleum.

I ask him about the Taj’s deterioration. He acknowledges the sad state of the river. But while he agrees that some of the marble is yellowing, he says that’s only natural. The ASI has been taking steps to clean it. Restorers first used chemical agents, including an ammonia solution.They now use a type of sedimentary clay called fuller’s earth. “It takes the dust and dirt from the pores of the marble, and after removing the impurities, [the fuller’s earth] falls down,” says Dixit. Some critics have derided this “spa treatment,” saying that fuller’s earth is a bleaching agent and will ultimately do more harm than good. But it’s used elsewhere, and when I later contact international conservationists to get their opinion, they tell me it’s unlikely to do damage.

There are many in Agra who believe that all the worries about the Taj are exaggerated—that far too much attention is paid to the monument at the expense of other priorities. They say the restrictions imposed upon the city’s several hundred brick kilns, iron foundries and glassworks to reduce air pollution have harmed the local economy. SM Khandelwal, a business leader in Agra who opposed Mehta’s legal campaign, has long argued that such businesses were responsible for only a tiny fraction of the fumes emitted in the city, and that the more significant polluters were vehicles and power generators. “I was very angry that everyone was so concerned about the Taj Mahal and not about the [livelihoods of the] people of Agra,” he says.

Even some international experts doubt that air pollution is the prime cause of the discoloring and pitting of the monument’s marble. At least some of the yellow marks on the monument, for instance, are rust stains from iron fixtures that hold the marble slabs in place. Marisa Laurenzi Tabasso, an Italian chemist and conservation scientist, has studied the Taj Mahal on behalf of international organizations and Indian authorities. “Most of the problems with the marble are not from pollution, but from climatic conditions,” she says. These include heat, sunlight and also moisture, which promotes the growth of algae, leading to biological decay of the stone.

Laurenzi Tabasso says the main human impact on the monument probably occurs inside the tomb, where the moist breath of thousands of daily visitors—and their oily hands rubbing the walls—has discolored the marble.

And the number of visitors is growing. Rajiv Tiwari, president of the Federation of Travel Associations in Agra, tells me that between March 2010 and March 2011, the number of people touring sites in the city jumped from an estimated 3.8 million to nearly five million.

The main concern, however, is the Yamuna River. Some of the activists I met in Agra cited arguments made by R. Nath, who has written dozens of books on Mughal history and architecture. Nath believes that the river water is essential to maintaining the monument’s massive foundation, which is built on a complex system of wells, arches—and, according to Nath—spoked wheels made of sal wood. Nath and some activists worry the groundwater levels beneath the monument are falling—partly the result of a barrier that was constructed upstream to augment public water supplies—and they fear the wood may disintegrate if it isn’t kept moist. Nath also believes the Yamuna River itself is part of a complicated engineering feat that provides thrust from different angles as the water wends its way behind the mausoleum. But, due to the lower water level, the Yamuna now dries up for months at a time. Without that stabilizing counterforce of flowing water, the Taj “has a natural tendency to slide or sink into the river,” Nath says.

A detailed survey of the Taj was carried out in the 1940s during British rule in India, showing that the marble platform beneath the mausoleum was more than an inch lower on the northern side, near the river, than on the south. Cracks were apparent in the structure, and minarets were slightly out of plumb. The implication of the study is disputed: some maintain that the monument was always a tad askew, and perhaps the minarets were tilted slightly to make sure they never fell onto the mausoleum. Nath argues that the Mughals were perfectionists, and that a slow shifting has taken place. A 1987 study by the Rome-based International Centre for the Study of the Preservation and Restoration of Cultural Property concluded there was no evidence of structural distress or foundation failure, but said there was “remarkably little information about the foundations and the nature of the subsoil.”

The report advised it would be “prudent to make a full geotechnical survey” and “highly advisable” to drill several deep boreholes to examine beneath the complex. A Unesco report in 2002 praised the upkeep of the monument, but repeated that a geotechnical survey “would be justified.”

When I asked ASI officials about the foundation, they said it was fine. “Geotechnical and structural investigations have been conducted by the Central Building Research Institute,” ASI director Gautam Sengupta told me in an e-mail. “It has been found...that [the] foundation and superstructure of [the] Taj Mahal are stable.” ASI officials, however, declined to answer several queries about whether deep boreholes had been drilled.

(Jeffrey Bartholet is a freelance writer and foreign correspondent)