Serres is one of the regional units of Greece. It is part of the Region of Central Macedonia. Its capital is the town of Serres. The total population reaches just over 175,000.GeographyThe mountains are Orvelos to the north, Menoikio to the east, Pangaio to the southeast, Kerdylio to the southwest, Vertiskos to the west, parts of Krousi to the west and portions of the Kerkini lies to the northwest. The regional unit borders on Thessaloniki to the southwest, Kilkis to the west, the Republic of Macedonia with the Novo Selo Municipality to the northwest, the Blagoevgrad Province of Bulgaria to the north, Drama to the northeast and Kavala to the east. The Strymonian Gulf lies to the south along with the Strymonas delta. Lake Kerkini was a lake located in the southern portion which is now drained. 41% of the regional unit are arable and most of the lands are near the Strymonas river which flows from Bulgaria and empties into the Strymonian Gulf. Another river is the Angitis in the eastern part of the regional unit, with the ravine and caves near Alistrati.