The Prabalgad Fort stands at an elevation of 2,300 feet (700 m) in the Western Ghats. The fort was previously known as Muranjan until it was taken over and renamed by the Marathaforces under Chhatrapati Shivaji Maharaj's rule. The fort has a Ganesh temple and some unidentified stone ruins. Its sister fort is Irshalgad. Right next to Prabalgad, to its north, lies the steep Kalavantin fort.
The Prabalgad Fort was built by the Bahmani Sultanate to keep an eye on the Panvel Fortand the Kalyan Fort in the North Konkan area. Around 1458 A.D, "Malik Ahmad" the prime minister of the kingdom of Ahmednagar, took over the fort during his conquest of Konkan. After disintegration of the Bahmani Sultanate, the fort remained with the Ahmadnagar Sultanate.
During the collapse of the Ahmadnagar Sultanate, Shahaji led a helping hand against the separate forces of the Mughal Empire and the Adil Shahi dynasty. After the collapse of the Sultanate, he moved to Muranjan along with his wife Jijabai and son Shivaji for a brief period of time.
However, following Shahaji's defeat and the agreement of Mahuli, North Konkan along with the fort, was ceded to Mughals who granted ruling authority of the area to Adilshah of Bijapur. Chhatrapati Shivaji conquered the fort from the Mughals in 1657 A.D, after which he established himself in the Kalyan-Bhivandi area.
During the attack by Chhatrapati Shivaji, The fort was governed by "Kesar Singh", a Mughal sardar, and was the only fort to put up a strong resistance. On seeing the signs of defeat, the women inside the fort performed Jauhar, a tradition of self-immolation to ensure an honorable and respectful death. Singh died during the battle in October 1657. Kesar Singh's mother hid herself and her grandchild during the attack. Chhatrapati Shivaji, in an act of kindness made sure the lady and the child were allowed a safe passage out.