Mannar Island, about 130 sq km in area, juts out into the Palk Straits towards India like a claw, creating a Gulf that is named after it. The island is connected to the mainland by a bridge and causeway some 3 km in length. The main feature of the town of Mannar is its Portuguese fort, which was erected in 1560. It has a four-sided design, with four bastions, a wet ditch on three sides, and an arm of the sea washing the fourth. The battlements are prominent and picturesque while travelling along the causeway from the mainland. The Dutch took it after a naval bombardment, strengthened it, but do not appear to have significantly altered it. 

Mannar Island, about 130 sq km in area, juts out into the Palk Straits towards India like a claw, creating a Gulf that is named after it. The island is connected to the mainland by a bridge and causeway some 3 km in length. The main feature of the town of Mannar is its Portuguese fort, which was erected in 1560. It has a four-sided design, with four bastions, a wet ditch on three sides, and an arm of the sea washing the fourth. The battlements are prominent and picturesque while travelling along the causeway from the mainland. The Dutch took it after a naval bombardment, strengthened it, but do not appear to have significantly altered it. 

The Mannar district features some exotic fauna and flora. The dugong, a marine mammal and distant relative of the elephant, lives in the shallow waters off the coast feeding on sea grasses. Dugongs probably gave rise to the mermaid legend, due to their vaguely human appearance while bobbing in the water with just their heads exposed, and tendency to suckle their young on the surface, holding them with their flippers in the manner of a woman with her baby. Sightings by European sailors of dugongs in the Gulf of Mannar in the 16th and 17th centuries no doubt strengthened the already widespread mermaid legend in the West.