An 18th century feat of engineering helped transform Bombay from seven small islands in the Arabian Sea into the megacity of Mumbai, India’s largest metropolis.
Known as the ‘Seven Islands of Bombay’, this hilly volcanic archipelago was earmarked by the British East India Company in the 18th century as a base for nautical trade across the Arabian Sea.
As Bombay began to grow into a major trading town, the population swelled with the influx of migrants from across India and more space was needed.
To solve the problem a major civil engineering project was proposed to join the islands together, known as the Hornby Vellard Project, after the British governor who commissioned it.
Work began in 1782 to connect the islands by draining creeks and constructing a series of causeways that would initially join the islands together; at the same time it was necessary to protect the land from being flooded at high tide.
Most of the 22 hilltops that made up the seven islands were razed and their debris was used to fill the gaps between the islands and to create a large sea-wall embankment around the low-lying areas.
The islands were all connected by the mid-19th century, but land reclamation continued until well after India gained independence in 1947.
The resulting landmass is known as Salsette Island, and is almost unrecognisable from the shape of the original archipelago it was built around.
The city of Mumbai occupies the southern peninsula of Salsette, wedged between harbours that fringe much of the coast, while the majority of the rest of the island is taken up by the Greater Mumbai Area.
Today, Salsette Island is the fourth most densely populated island in the world, inhabited by both the metropolis of Mumbai and the city of Thane on its northeast corner.