Delhi’s history is often spoken of in terms of its seven cities. These were fortified settlements, established by various rulers between the 11th and 17th centuries, now swallowed by the sprawling city of today. The sixth Delhi is the Purana Qila, or Old Fort, a 16th-century stone fort near the eastern edge of the city, and a particularly good place from which to tell the story of Delhi’s urban development.

There are monuments in Delhi older than the Qila – and there are certainly more impressive ones. But it’s unlikely there exists another place in the city where history runs as deep. Excavations in the fort show the area was inhabited in five preceding Delhis, and even earlier, reportedly back to 300 BC. Some also believe that somewhere under the Qila are the remains of a legendary city that’s a civilisational navel of sorts. The aura of this city – Delhi zero? – has enticed kings and governments and allowed it to maintain its curious influence over the city’s evolution.

The walls of the Qila, and the few structures within – a stepwell, a squat tower used as a library-cum-observatory, and a fine mosque – are attributed to the Mughal emperor Humayun and the Afghan Sher Shah Suri (‘The Lion King’), rivals who ruled Delhi in the mid-16th century. Humayun’s construction began in 1533, but was deposed after a few years by Sher Shah. Humayun recaptured the fort 15 years later, but soon after tripped down the stairs of the library and died. A Mughal chronicler from the time mentions that Humayun’s fort was built on the hallowed site of Indraprastha, a story that sits in the shimmering realm between myth and history.

Indraprastha appears in one of India’s foundational Sanskrit epic poems, the Mahabharata, as the capital city established by its heroes, the Pandava brothers. What better way for a ruler to claim legitimacy than to rule from this proto-capital?

The Qila was forgotten for a while after Humayun’s rule, then remembered by the British. They decided to move the capital of colonial India from Calcutta to the more central city of Delhi in 1911. Charles Hardinge, viceroy of India, had argued in favour of Delhi as it would please both Hindus – for its traditional association with Indraprastha, and Muslims – for its connection to the Mughals.

The plans for the administrative capital of New Delhi were made by Edwin Lutyens, who saw to it that the eastern end of the ceremonial avenue (Kingsway then, Rajpath now) aligned with the Purana Qila. The Viceroy’s House (now the president’s residence) was built at an elevation so it would look upon the old fort and establish a symbolic connection.

The Qila was a living part of the city until 1914, when a village within the fort walls was found incompatible with the Qila’s new-found grandeur, and was cleared. Later, the fort became the site of several temporary settlements. During the second world war, there was a camp of nearly 3,000 Japanese civilians from across British-ruled Asia. After the partition of India in 1947 and the ensuing violence, the Qila sheltered thousands who were fleeing Delhi, as well as those who had moved there. Some of these new settlers remained until the early 1960s.

From then on, the Qila has stood in a landscaped stupor. Today, the fort is surrounded by a zoo, and the moat is a spot for boating and zorbing. Aside from history enthusiasts and couples seeking privacy from the crowded city, few enter the red sandstone gate between the fort’s stout bastions.

As an independent nation Indian archeologists have remained enchanted by the chance to uncover signs of the mythical Indraprastha. The Archaeological Survey of India embarked on several digs in the Purana Qila, but they have not been successful. In the process, archaeologists have turned up artefacts from every period dating back to 300 BC, around when the city of Delhi is believed to have been founded. Remains of fortifications that pre-dated Humayun’s rule have been found – other kings at other times, perhaps struck by the same idea.

Myth or reality, the idea of Indraprastha is now embodied in the Purana Qila, and together they have borne witness to some of the most significant moments in the history of India’s capital.