The largest lake in  Attiki  is that of Marathonas. It is an artificial reservoir originally created for the Athens water supply. It is sourced from and named after the natural lake which used to exist nearby. In August or September of490 BC, the famous battle of Marathon took place at the surrounding area  where the Greeks were able to defeat the numerically superior Persian army and force it to flee. Today the lake, with a depth of 54 meters covering an area of ​​2,450 square km, fosters a rich ecosystem, while the basic water supply of the city of Athens now comes springs from the newly made artificial lake of Mornos.