Sérres (Greek: Σέρρες [ˈseɾes]) is a city in Macedonia, Greece, capital of the Serres regional unit and second largest city in the region of Central Macedonia, after Thessaloniki. Serres is one of the administrative and economic centers of Northern Greece. The city is situated in a fertile plain at an elevation of about 70 metres (230 feet), some 24 kilometres (15 miles) northeast of the Strymon river and 69 km (43 mi) north-east of Thessaloniki, respectively. Serres' official municipal population was 76,817 in 2011 with the total number of people living in the city and its immediate surroundings estimated at around 100,000.