Varanasi

These include Gyanvapi and Shahi Eidgah, two disputed mosques in the holy cities of Varanasi and Mathura.

“Biofilms are known to cause mechanical failures,” says Kripa Varanasi at the Massachusetts Institute of Technology.

Prof Varanasi and his colleagues have developed a range of coatings that make surfaces slippery and therefore resistant to the formation of biofilms.

Prof Varanasi has previously made headlines for developing similar coatings for the insides of toothpaste packets – so you can get every last bit of toothpaste out.

PM Modi is seeking a third term as an MP from Varanasi, popularly known as Benaras or "the world’s oldest living city".