The prefecture of Attica is located at the southernmost point of central Greece. The mainland Attica without the island section make up the Athens metropolitan area. The population of Attica region is about 4 million people. Attica is well-known because of Athens, the capital of Greece. The great history of Greece is connected with Athens, where the notion of democracy was invented. Attica is a peninsula sticking out into the Aegean Sea. It is physically divided to the north from Boeotia by the 10 mile long Kithairon mountain range. The peninsula is separated by mountains into the plains of Pedia, Mesogeia, and Thriasia. The mountains include Hymettus, the eastern portion of Geraneia, Parnitha, Aigaleo and the Penteli mountains. To the north it is bordered by the Boeotian plain and to the west it is bordered by Corinth. The Saronic Gulf lies to the south and the island of Euboea lies off the north coast. Athens' first and only large reservoir was opened in the 1920s called Lake Marathon Since that time, it has been Attica's largest lake. Forests cover the area around Parnitha, around Hymettus and into the northeast and the north in the hills and the mountains, except for the mountaintops, but the mountains to the west and the south are grassy, desolate or forested.