The Katavothres (literally holes that swallow) are an extremely rare geological phenomenon. The seawater rushes in wells under the sea level. This move has allowed in the past to create water mills.
The entrance is located at the north end of the peninsula of Argostoli. An interconnected network of caves beneath the mountain is filled with sea water. The winter rains seep into the rock and mix with the sea water.
The system ends at Sami on the other side of the island where the water is discharged into the lake of Karavomilos.