A caver viewing the light entering the Tham Mae Usu cave in Northern Tak province, Thailand. The cave is only accessible during the dry season in Thailand as the main entrance is through a flooded tunnel that the Mae Usu river flows out of in this limestone karst cave, making it impassable throughout most of the year. The cave is named after a folklore tale of a nobleman's pregnant wife. The tale is that whilst she and her husband were fleeing persecutors they happened upon the cave and rested. She believed that in her pregnant state she would slow the fleeing party down and the persecutors would capture them and them kill so she elected to remain in the cave to allow her husband and extended family to escape.