Restoration work on a lesser known tomb in the heart of the city has led to the discovery of the country's oldest “sunken garden”, a serendipity that will put the history of the Mughal gardens in a new perspective.

Restorers at the Isa Khan's tomb in the precincts of the Humayun's Tomb World Heritage Site have discovered that the Isa Khan's tomb stood within a hitherto unknown sunken garden that predates the famed gardens that the Mughals built and popularised. Also uncovered at site are pieces of underlying archaeology.

And with this discovery, the country now has a new chapter added to the history of the Mughal gardens.

“It is an important discovery as the Isa Khan's Tomb garden predates the Humanyun's Tomb garden by two decades. It is also very significant as Isa Khan's garden tomb can now be considered the earliest example of a sunken garden in India – attached to a tomb – a concept later developed at Akbar's Tomb and at the Taj Mahal,” said Ratish Nanda, Project Director of the Aga Khan Trust for Culture, that has been undertaking an urban renewal project in the Humanyun's Tomb Nizamuddin Basti area.

“We were not expecting to discover that the earth levels in the enclosure were over a metre lower than the existing levels, when we began the restoration of the Isa Khan tomb. We realised that the level of the garden, as was designed originally was much lower than its existing level. So we began the work of restoring the garden to its original design,” he added.

The restoration work of the Isa Khan's Tomb is being carried out by the AKTC in partnership with the Archaeological Survey of India and with co-funding from the World Monuments Fund.

The ongoing restoration work has thrown up underlying archaeology, including building elements such as finials of the dome and canopies and terracotta toys, all of which have immense historical relevance.

Referring to the work that has been underway for the past eight months, he said: “Once we discovered that the garden was much lower than what it had risen to, we had to begin earth moving work. And since we were operating in an area rich with underlying archaeology, we could not use machines, and everything had to be done manually. Over 3000 cubic metre of earth was removed to restore the garden to its original level.”

Over 20,000 man-hours later, the AKTC team today is in the middle of restoring the garden and the tomb that it circumferences to its original glory.

After a peer review, with national and international experts, before the onset of works from July – December 2010, restoration work began with test pits being created that revealed the original levels to be 1m lower than existing levels. Restorers also found parts of building elements such as columns of the tomb's dome and finials buried in the garden that are now being used for its restoration.

“It is an exciting and a wonderful discovery. The sunken garden here has revealed how the gardens have risen over the years, just as layers are added to history; layers have been added to the gardens as well. Over the years gardens have come up at the level of the monuments, but this garden has revealed that here it was originally three to four feet below the monument with the tomb sitting high,” said Amita Beg of the WMF.

The discovery has also shed light on the grandeur of the tombs, rising above the gardens and overlooking the trees and the landscaping. “By placing the tomb higher than the garden, not only was the magnificence of the tomb enhanced, but it would also allow visitors to the tomb to be at eye level with the surrounding tree species such as citrus varieties popularly used by the Mughals,” said Mr. Nanda.

Isa Khan finds mention in history as a brave and valiant noble under Sher Shah Suri, the Afghan ruler who had overthrown Humayun. The tomb built in 1547 is octagonal in shape and has exceptional decorative detailing.