Katavothres is situated just outside of Argostoli on the coastal road to Lassi. The area has recently been revamped and there is now an attractive bar along the watermill. From way back in time people have known about the swallow holes (katavothres) . An unusual geological phenomenon, the seawater pours through craters in the rocks near the shoreline and disappears underground. An Englishman named Stevens, was the first to notice this occurrence, and was so impressed that he built water mills there.
Some time later, during the severe 1953 earthquakes, 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. Not long prior to the 2nd World War, the mills were in use and served also as an ice factory. Many attempts have been made to explain the phenomenon. Various theories were put forward .
In 1963 Austrian geologists carried out systematic and efficient research. They poured 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.
The roof of the Melissani Cave has fallen in over the years due to earthquakes, Kefalonia is prone to these, and the waters of Karavomilos form a lake in the cave. At its deepest point, the lake is 32 meters deep and it is famed for its crystal-clear waters and the ever-changing shades of blue and green that can be observed at different times of the day. It looks stunning at midday when the sun is overhead. During the research it was revealed that the water that vanishes at Katavothres near Argostoli, oozes out at the village of Karavomilos near Sami, forming a nearly completely circular fresh-water lake, which empties into the sea in Sami Bay. The journey from Katavothres to Sami Bay takes 14 days.