“Here, it is not the river god of the nymphs who holds way
But great Poseidon himself who invades the kingdom of the earth”. (Ansted).

  From time immemorial people have known about the swallow holes (katavothres) just 2.5km out of Argostoli. A rare geological phenomenon, the seawater pours through cracks in the rocks near the shoreline and disappears underground.
The Englishman, Stevens, was the first to notice this phenomenon, and was so impressed that he built water mills there. The famous geologist, Miliaresis, studied the effect of earthquakes on the phenomenon during the same period. He observed that even during large earthquakes, like the one in 1867, the mills continued to work unhindered and there was no change whatsoever to the flow of the current.
Later on, during the severe 1953 earthquakes, again there was no change to the flow of the sea at the swallow holes or sea mills. The only thing that was destroyed was the water wheel, which was replaced by the one there today. Shortly before the 2nd World War, the mills were actually in use and served also as an ice factory. Many attempts have been made to explain the phenomenon. Various theories were put forward as explanations: Ansted put forward the cave theory in 1835, later in 1842 the geologist Davy linked the phenomenon to earthquakes, and Strickland proposed the plutonium theory. No one, however, came close to explaining the phenomenon.
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  It was only in 1963 Austrian geologists carried out that systematic and efficient research. They poured an amount of dye into one of the sink holes, which eventually came out into the sea at the village of Karavomilos, and confirmed their findings by following up, with radioisotopes. These same researchers followed the trail of the water and discovered that it moves NW under the ground, crosses the island and, on its way, mixes with the rainwater from the water table. In this way it gathers speed, re-emerging into daylight at Melissani Lake.
  In Melissani Cave most of the roof has fallen in over the years because of the many earthquakes the island is prone to, and the waters of K aravomilos form a lake in the cave. At its deepest point, the lake is 32 meters deep and it is renowned for its crystal-clear waters and the ever-changing shades of blue and green that can be observed at different times of the day. The same research work revealed that the water that vanishes at Katavothres in Argostoli, gushes out at the village of Karavomilos near Sami, forming a nearly completely circular fresh-water lake, which empties into the sea in Sami Bay.


  1. The seawater goes underground at Katavothres in Argostoli.
  2. The seawater goes under the harbour and the mountains of the island.
  3. The rainwater table.
  4. The seawater mixes with the rainwater.
  5. The brackish water flows into Melissani Cave and into Karavomilos Lake at Sami.


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