Humayan’s Tomb in New Delhi, a UNESCO World Heritage site, is under threat from unpredictable rainstorms, air pollution and slow upkeep after standing for 500 years. Polluted water seeping into the structure threatens to weaken it from within. “It’s almost like our skin – the skin is porous. (If) you put cling film around it, the cells start dying out,” said Ratish Nanda, CEO of the Aga Khan Trust for Culture in India, an organisation involved in cultural revitalisation and heritage conservation. “Buildings which are generally meant to breathe with water – (their) pores are being closed. The water is being retained in the sandstone or in the masonry. It’s a cocktail of reactions that are difficult to predict,” he added. Humayun’s Tomb is one of more than 70 historic sites in central Delhi that the organisation is conserving. The effort has drawn on specialist craftsmen from Uzbekistan to painstakingly revive traditional techniques and lost details – a “labour of love etched in rock”, as described by Nanda.