Vijaydurg Fort Vijaydurg ( sometimes written as Viziadrug ) , the oldest fort on the Sindhudurg coast , was constructed during the regime of Raja Bhoja II of the Shilahar dynasty ( construction period 1193 - 1205 ) . The fort was earlier known as " Gheria " , as it is situated close to the village of " Girye " . Shivaji captured this fort from Adil Shah of Bijapur in 1653 and renamed it as " Vijay Durg " as the then Hindu solar year ' s name was " Vijay " ( Victory ) . Earlier , the fort encompassed an area of 5 acres ( 1 acre = 4840 square yards or 4047 square metres ) and was surrounded by sea on all four sides . Over the years the eastern trench was reclaimed and a road constructed thereon . Presently the area of fort is about 17 acres and is surrounded by the Arabian Sea on three sides . Shivaji extended the area of the fort by constructing three walls on the eastern side , each 36 metres high . He also constructed 20 bastions . According to legend , this is one of only two Maratha forts where Shivaji personally hoisted the saffron flag . The other fort is " Torana " . Vijaydurg Fort was called the " Eastern Gibraltar " , as it was virtually impregnable . Its locational advantages include the 40 km long Waghotan / Kharepatan creek . Large vessels cannot enter the shallow water of this creek . Also , Maratha warships could be anchored in this creek and yet remain invisible from the sea . It is a protected monument . Location . Located in Devgad Taluka , Vijaydurg and its surroundings are famous all over the world for the delicious Alphonso mangoes . During the growing season , the smell of mango blossom hangs heavy in the air . Mango plantations are everywhere ; along with fishing and farming , mango cultivation is a primary occupation of the people in Devgad . Features of Architectural Interest . 1 ) According to unconfirmed reports , there is a 200m long , undersea / underland tunnel from the fort to the palatial Dhulap house in the village . Supposedly , the roof of the tunnel has been pinched to protect it from landslides and it is also well ventilated . Now the tunnel is partially blocked . If the presence of the tunnel can be confirmed , and the tunnel cleared , it could serve as a tourist attraction of historical and architectural interest . 2 ) Recent oceanographic evidence supports the existence of an undersea wall , constructed out at sea at a depth of 8 – 10 m depth undersea . Made of laterite , the wall is estimated to be 122 mtrs long , 3 mtrs high & 7 mtrs broad . Attacking ships often met a watery grave after colliding against this wall . 3 ) 1 . 5 km from the fort up the Waghotan Creek , exist the remains of a naval dock carved from rock . This is where Maratha warships were built and repaired . The ships built here were of the 400 - 500 tonnage capacity . This 109 * 70 mt dock faces the north side and is an achievement of Maratha naval architecture . Other facts . 1 ) Sir J Norman Lankier , a British scientist was observing a solar eclipse from this fort on 18 August 1868 . It was during his observation that the Helium Gas was discovered on Sun in the form of a yellow flame ! He named this as Helios which was later named as Helium . Vijaydurg can be credited as the place from where , Helium was discovered and observed on sun . 2 ) The fort has many monuments , now in ruins which show the characteristics of Maratha architecture . The food storage go - down and court are such classic examples .