Why do the Taj Mahal's minarets lean outwards?

So that if one fell it would fall away from the tomb. All four are tilted very slightly outward from the plinth - close to imperceptible from the ground - which is a deliberate precaution in an earthquake zone, protecting the mausoleum at the cost of the towers.

The rest of the engineering is equally careful and less visible. The complex sits on a series of wells filled with rubble and topped with timber, which spreads the load across soft ground by the Yamuna and copes with movement. That is now the source of real concern: as the river runs lower, the timber is exposed and may be drying and decaying, and there have been repeated warnings about the foundations.

The marble is also going yellow. Particulate pollution from vehicles, industry and crematoria along the river discolours the surface, and it is periodically cleaned with a clay poultice - the same treatment used for a facial - applied and peeled off. India has closed and moved industry around Agra by court order to slow it, with mixed success.