The bridge is 18 miles (30 km) long and separates the Gulf of Mannar (southwest) from the Palk Strait (northeast). Some of the sandbanks are dry and the sea in the area is very shallow, being only 3 ft to 30 ft (1 m to 10 m) deep in places, which hinders navigation. It was reportedly passable on foot up to the 15th century until storms deepened the channel: temple records seem to say that Rama’s Bridge was completely above sea level until it broke in a cyclone in 1480 CE.
A 19th century painting depicting a scene from Ramayana, wherein monkeys are shown building a bridge to Lanka
The ape-army building the bridge. Illustration by Balasaheb Pandit Pant Pratinidhi from a 1916 edition of the Ramayana epic
The bridge was first mentioned in the ancient Indian Sanskrit epic Ramayana of Valmiki. The name Rama's Bridge or Rama Setu (Sanskrit; setu: bridge) refers to the bridge built by the Vanara (ape men) army of Lord Rama in Hindu mythology, which he used to reach Lanka and rescue his wife Sita from the Rakshasa king, Ravana. The Ramayana attributes the building of this bridge to Rama in verse 2-22-76, naming it as Setubandhanam, a name that persists till today.
The sea separating India and Sri Lanka is called Sethusamudram meaning "Sea of the Bridge". Maps prepared by a Dutch cartographer in 1747, available at the Tanjore Saraswathi Mahal Library show this area as Ramancoil, a colloquial form of the Tamil Raman Kovil (or Rama's Temple). Another map of Mughal India prepared by J. Rennel in 1788 retrieved from the same library called this area as "the area of the Rama Temple", referring to the temple dedicated to Lord Rama at Rameswaram. Many other maps in Schwartzberg's historical atlas and other sources such as travel texts by Marco Polo call this area by various names such as Sethubandha and Sethubandha Rameswaram.
The western world first encountered it in "historical works in the 9th century" by Ibn Khordadbeh in his Book of Roads and Kingdoms (ca. 850 CE), referring to it is Set Bandhai or "Bridge of the Sea". Later, Alberuni described it. The earliest map that calls this area by the name Adam's bridge was prepared by a British cartographer in 1804, probably referring to an Abrahamic legend, according to which Adam used the bridge to reach a mountain (identified with Adam's Peak) in Sri Lanka, where he stood repentant on one foot for 1,000 years, leaving a large hollow mark resembling a footprint.
Adam's Bridge starts as chain of shoals from the Dhanushkodi tip of India's Pamban Island and ends at Sri Lanka's Mannar Island. Pamban Island is semi-connected to the Indian mainland by 2 km long Pamban Bridge. Mannar Island is connected to mainland Sri Lanka by a causeway. The border between India and Sri Lanka is said to pass across one of the shoals constituting one of the shortest land borders in the world. Adam's bridge and neighbouring areas like Rameswaram, Dhanushkodi, Devipattinam and Thirupullani are mentioned in the context of various legends in Ramayana.