When the refugees from Asia Minor arrived, there was a big population increase, and the need for running water exploded. The construction of a dam in the village of Marathonas was the answer. The American company Ulen signed as the contractor for the development of the dam.
The dam is located 223 m. above sea level and is 54 m high and 285 m. long. Its width is 4,5 m. at the top and 28 m. at the base. Its depth is 54 m.
Some of its structural parts are decorated with marble from the mountain of Pendeli in a symbolic gesture to link it to Parthenon, which is made of the same marble.