Reitoi were two small artificial lakes on the west foot of Mt Aigaleo. Their springs were in natural cavities, which were blocked in antiquity. The stream outlets to the sea were crossed via bridges. Before these works the
place had been a swamp and impossible to cross. The water had salt, due to its proximity to the sea.
The north lake was devoted to Demeter and the south to Persephone. The latter is preserved until today and
is called Lake Koumoundourou. It marks the border between Chaidari and Aspropyrgos, and it used to be the boundary between Athens and Eleusina. I. Traulos recognized that some of the building blocks of the dam came from the Peisistratian sanctuary at Eleusina, which was destroyed by the Persians in 479 BC. An inscription
of the Athenian Boule of 421 BC, now in the Museum of Eleusina, mentions the construction of a bridge 1.5 m wide, hence for pedestrians only.
Both streams and lakes had been preserved until the 19th century and featured two water mills, noted by François Pouqueville, while Gustave Flaubert saw only a swamp. Until the 1950s both lakes were natural fish reserves. The south lake was named either after the local land owners, or prime minister Alexandros Koumoundouros (1817-1883), responsible for road building in the area during the 1860s. The post-World War II widening of the national road reduced the size of the lake significantly. The north lake, Kephalari, was backfilled during the construction of the oil refinery at Aspropyrgos. Its place is today marked by a swamp.