The artificial Lake of Marathon is a lake created to collect water for the supply of Athens. It's formed by the construction of Marathon Dam at the function of the streams Charadros and Barnabas and a few kilometers from the town of Marathon, Attica.

The Marathon Lake was the main water reserve for the supply of Athens since 1931, when it started to give water until 1959. In 1959 work began to supply connection from Yliki Lake, while since 1981 most of the water to irrigate the Greek capital comes from the artificial lake of Mornos. Today all water in Marathon's Lake wuld not be sufficient only for a few days in Athens water supply.

Dam Marathon Construction in 1930

The extent of the lake with water in the weir height is 2.45 tetr.kilometers (2450 acres) and its maximum dept is 54 meters. The lake collects water from an area called basin, 118 sq km extent km, with an average yield 14.400.000m3 per year with average annual rainfall of about 580 mm. The average volume of the lake is 12.000.000 m2, while the maximum volume (capacity) is 41.000.000 m3 (of which can be distilled 34 million).

The dam's top is located at an altitude of 227 meters above sea level and the foot (base) at an altitude of 173 meters. However, the spilway lies at an altitude of 223 meters and this is the maximum altitude of the surface of the lake above the sea level. The spilway's provision is 520m3/sec . The dam was constructed by the American company ULEN (which kept under the contract ownership of water companies in the capital until 1974). The dam lasted from 1926 to 1929.