Jacob's Well -- Wimberly, Tx: One of the most significant natural geologic treasures in the Texas Hill Country. It is one of the longest underwater caves in Texas and an artesian spring. Jacob’s Well surges up thousands of gallons of water per minute!
To Sua Ocean Trench in the Lotofaga village on the south coast of Upolu, Samoa. o Sua is a giant hole in Lotofaga that was converted into a swimming pool with water flowing through a lava-tube tunnel. WANT TO GO!