In 1516, A local chieftain in Gujarat, Sultan Mahmud Begda originally constructed the fort on the island, strategically located at the mouth of the Vaitarna river. In the 1530s, the Portuguese had established their operations in the coastal area headquartered at Fort Bassein and soon gained control of the island. The Portuguese captain of Bassein donated the island to a Portuguese nobleman who tore down the old fort and began construction of 700x700 foot fort. Though fort was never completed by the nobleman, it remained under Portuguese control for 2 centuries, who used it to control shipping and navigation along the northern Konkan coast.
During the late 1600s and early 1700s, after a long struggle with the Mughal empire, the Maratha Confederacy came to dominate present day Maharastra. In 1737 the then Peshwa Baji Rao I sent his brother, Chimaji Appa, to take the Bassein Fort from the Portuguese. After winning the Battle of Vasai, his general, Shankarji Pant, persuaded Chimaji to launch an assault on Fort Arnala, for its strategic importance to the Maratha navy in assaulting Portuguese interests. Their first assault, coordinated with a Maratha naval force commanded by Manaji Agre, was routed by a superior Portuguese naval force. A second assault on the fort on March 28, 1737, caught the Portuguese by surprise and forced them to abandon the fort. The victory was commemorated by a plaque installed on the northern wall of the fort and is still visible today. Marathas then rebuilt the fort, constructing three bastions Bahirav, Bhavani and Bava.
The Marathas controlled the fort until 1817 when, during the third British-Maratha war, despite successfully defending the fort, they where forced to surrender the fort to the British due to their superior naval power. The Arnala and Bassien forts were returned to the Marathas by the British in the treaty of Salabai, but the forts again changed hands under the treaty of Pune.
Today the fort is in a state of disrepair.
How to reach
Buses from Virar railway station will bring you to Arnala a (short distance of 25 mins). From the Arnala market you will have to traverse through the small fishing village of Arnala to reach the sea shores. From here its only the small trawlers that can carry you to the Fort Island.
Other things to see
There is a beautiful Kalikamata temple on the shores of the fort island. Every year over a lakh devotees throng the temple for offering prayers & sacrifices on the auspicious day of Dasera.
Located in the premises of the Arnala Fort, the temple has humble origins. Even though there is lack of mention about the temple in the history books, it is believed that the idol of Goddess Kalika Mata was found in 1516 when the work for Arnala Fort was on.