The Taj Mahal is getting a mud bath! India’s famous marble monument is located near New Delhi, one of the country’s most crowded cities. Air pollution in the region has turned the white stone yellow and black.

Workers are covering the building with special clay. This clay soaks up grime from the stone. After the mud dries, workers wash it off to reveal the clean white surface.

But the monument may not stay white. “The only way to keep the Taj Mahal clean long-term is to stop the pollution,” says environmental scientist Ajay Nagpure.