Now conservationists have restored the grounds of the massive bulbous-domed tomb of Mughal Emperor Humayun who plunged down a stairway to his death in 1556 rushing to answer the Muslim call to prayer.
Long-dormant fountains in the garden have come to life for the first time in some 400 years and water flows through narrow canals representing the four rivers of paradise described in the Koran.
"The garden was in a dismal state when we started the restoration (two years ago)", said conservation architect Ratish Nanda as cries of starlings pierced the sultry late afternoon heat and peacocks strutted idly across green lawns.
As the conservation architects worked, the stark symmetry of the char-bagh or four-part garden, became clearer, he said.
Workers had to hack away weeds which had choked paths and clean up dust-silted waterways around the sepulchre whose harmonious, classic proportions are seen as the architectural precursor of the Taj Mahal, the monument to love.
But getting the water to circulate again was "the most difficult challenge by far" facing engineers, Nanda said.
The problem lay in the gradient of the waterways dividing the garden into four quadrants. The channels, which run on a gravitational principle, have a drop of just one centimetre (0.4 inches) every 40 metres (130 feet), making restoration of the water flow a high-precision job.
Four attempts to get the water going were made in the last century but they failed. "It shows the genius of the Mughals that it took so long to replicate their achievements," Nanda said. "We solved the problem only with the help of extremely sophisticated survey equipment."
The dusky-red mausoleum was built in 1560s by Humayun's son, Akbar, who went on to build an empire stretching from modern-day Afghanistan to parts of southern India and is revered for his tolerance toward all faiths.
"But by the early 1600s it (the tomb) had gone into neglect", Nanda said, after Akbar shifted the Mughal capital in 1599 to Agra, site of the Taj Mahal.
The Taj Mahal was built by Akbar's grandson, Shahjahan.
The Mughals, famed for their architectural splendours, are one of the Indian subcontinent's great dynasties.
FAITHFUL TO CRAFT
Work on the $650,000 restoration of Humayun's Tomb, sponsored by the Aga Khan Trust for Culture and the Archaeological Survey of India, began in 2001 and the conservationists tried to be faithful to Mughal craftsmanship. The only new addition was a pump for a water recycling system.
Sixty stone-cutters, using centuries-old skills, chiselled slabs to repair the paths and canals of the garden.
Now also thousands of mango, lemon and pomegranate trees and sweet-smelling hibiscus and jasmine plants -- favourites of the Mughals -- have been planted on the site, an oasis of calm not far from a never-ending stream of honking traffic in New Delhi.
The garden with its pools, plants and trees is meant to symbolise paradise and is believed to be the earliest example of an imperial garden tomb on the Indian subcontinent, scholars say.
"The bicycle rickshaw was the most sophisticated vehicle we used to cart away 3,000 truckloads of earth" that had hidden the 30-acre (12 hectare) garden's original contours, Nanda said.
But conservationists were unable to make the garden look exactly the way it did in Mughal times as the earliest known drawings date from the 19th century. They had to turn to written records for help.
The tomb fell into obscurity as Muslim power waned. In fact, by the 1790s, the tomb and surrounding areas had been abandoned. Thomas Twining, a British traveller of the era, chanced upon it then but said he "could find no human being to inform me what king or prince had received this costly sepulchre".
The conservation architects retained parts of the garden introduced soon after the turn of the 20th century when the British ruled India, such as stone benches on which to rest and gaze at the tomb's imposing contours.
"The Taj is like a great dreamy palace of a king while Humayun's tomb is much simpler but very elegant. Its serenity makes it a place of peace and tranquillity," said O.P. Jain, a leading voice for conservation of Indian monuments.