Tanintharyi is the southernmost region in Myanmar, and lies south of Mon state. It is a long narrow region on the Kra Isthmus. It borders the Andaman Sea to the west and the Tenasserim Hills, in fact the region was known as Tenasserim during the British days. To the east is Thailand - the border areas are not accessible to foreigners.
There are many limestone islands off the coast and birds nest caves are common.
For more information on the caves, see BHB 39.