Adam's Bridge or Rama Setu

Adam's Bridge, also known as Rama Setu, is a chain of natural limestone shoals between  Rameswaram Island, off the south-eastern coast of  Tamil Nadu and Mannar, off the north-western coast of Sri Lanka. Geological evidence suggests that the bridge was formerly a land connection between India and Sri Lanka.

The feature is 48 km long and separates the Gulf of Mannar from the Palk Strait. Some regions of the bridge are dry, and the sea water in the area rarely exceeds 1 metre  in depth, making it quite difficult for boats to pass over it.

In the Book of Ibn Khoradadbeh, a Persian Geographer (c.850) the structure is referred to as Set Bandhai meaning Bridge of the Sea. Al-Biruni’s Tārīkh al-Hind (c. 1030) was probably the first to use the name Adam's Bridge This appears to have been premised on the Islamic belief that Adam’s Peak where the biblical Adam fell to earth — is located in Sri Lanka, and that Adam crossed over to peninsular India via the bridge after his expulsion from the Garden of Eden

The ancient Sanskrit epic Ramayan mentions a bridge constructed by the God Ram to reach the island Lanka and rescue his wife Sita from Ravana. In popular belief, Lanka is equated to present-day Sri Lanka and the bridge is described as "Rama's Setu".

The bridge starts as a chain of shoals from the Dhanushkodi tip of India's Pamban Island. It ends at Sri Lanka's Mannar Island. Pamban Island is accessed from the Indian mainland by the 2-km-long Pamban Bridge. Mannar Island is connected to mainland Sri Lanka by a causeway.