Salsette Island consists of a number of smaller islands lay on its western flank, located west coast of Maharashtra, India. The island comprises Mumbai city, Thane and Mira-Bhavandar and bustling with an estimated 15.1 million inhabitants making the island one of the most populous islands in the world. Spreading over an area of 19 km^2 and consists of black basalt rock, the island is enclosed on the north by Vasai Creek, on the northeast by Ulhas River, Thane Creek and Bombay Harbour are situated on its east part and its southern part is engulfed by mighty Arabian Sea. The island is at the confluence of a number fault lines and makes the whole region earthquake-prone up to a magnitude of 6 rector scale.

The Salsette island is dominated by hills and small mountain surrounded by tidal flats. Since the island is situated along the sea shore, it has a sandy belt on its western coast and its southern region is mostly at the sea level. On its western side a number of small islands including Bandra, Juhu Dharavi Island, Rai Murdhe along with sandy beaches lay on. Till 1808 these islands remained detach and at the time of writing the old Gazetteer of Thana in 1882 the islands were put together and joined to Salsette via reclamation. The Island includes Borivali National Park and the conical peak of Kanheri with an elevation of 467 meters from the ground. The Borivali National Park is known as the world’s biggest park within city limits and enormous tourists visit the park every day.

The original seven islands of Bombay which were merged by land reclamation during 19th century, once the island was occupied by famers, agricultures, artisans and fishermen. Later on arrival of father St. Bartholomew the local inhabitants were converted to Roman Catholicism. The island was subjugated and ruled by several Hindu kingdoms, the last of which were the Silharas. In the year 1343, the island was conquered by the Muslim of Gujarat and later in 1543 Portuguese grabbed the island from Bahadur Shah of Gujarat. Finally in the year 1774, British took the control of the Island and ceded to the East India Company as per the Treaty of Salbai (1782). After the treaty William Hornby, then Governor of Bombay commenced the project of connecting the islands and by 1845 the seven islands had been connected to form old Bombay (presently Mumbai city). Since then the accessibility considerably increased among the seven islands and by 1901 the populous Salsette region was started considering as Greater Bombay.

Presently The Salsette Island includes 109 Buddhist caves dated back to 2nd century and the caves are similar in structure to that of Kanheri caves.  In addition, the island houses several lakes: Powai Lake, Tulsi Lake and Vihar Lake are major; Rivers like Mithi, Poisar, Oshiwara etc. A number of brackish creeks extend inland from coast line. The Mahim creek splits the city from the suburbs in the west. The huge protected northern wetlands of Salsette Island are bustling with innumerable species of migratory birds and dense mangroves forests.