The Aga Khan Foundation has been active in conserving India's cultural heritage.

A prominent project has been the Humayun garden tomb, an exquisite 16th-century monument widely regarded as the precursor of the Taj Mahal.

After six years of work by hundreds of master craftsmen using the same materials and methods from the time, the tomb was reopened in 2013.

The foundation, funded by private donations, then started work on the surroundings, restoring the Sunder Nursery by revitalising the pathways, fountains and water channels of the "paradise garden". Now it is involved in restoring the nearby neighbourhood of Nizamuddin Basti, significant for its Muslim culture and traditions.

Rarely do private individuals put money into conservation, but New Delhi MP Vijay Goel, who represents the Chandni Chowk constituency in Old Delhi, has restored a crumbling 150-year-old "haveli" (a mansion built by Muslim nobles) to its original splendour. "When I bought it some years ago, my friends warned me against it. They said it would be a disaster."

Many havelis in Old Delhi have been turned into warehouses. Goats and dogs roam around what used to be beautiful, colonnaded courtyards that led off into rooms where several generations of the same wealthy family lived.

Mr Goel said: "There used to be a lot of money here. While restoring it, we found a secret basement that was probably used as a storehouse for gold." In the restoration, he used only materials that the original owners would have had access to.

Called Haveli Dharampura, the building now reminds residents of the former glory of Chandni Chowk. After all, this is where the colossal Red Fort and Jama Masjid, built by Mughal emperor Shah Jehan, are located.

The former princes all over India, too, have taken great care to preserve their forts and palaces. After losing their titles and privy purses in 1971, they had to turn their palaces into hotels to survive.

Amrit Dhillon