Vidin Province (Bulgarian: Област Видин) is the northwesternmost province of Bulgaria. It borders Serbia to the west and Romania to the northeast. Its administrative centre is the city of Vidin on the Danube river. The area is divided into 11 municipalities. As of December 2009, the province has a population of 108,067 inhabitants. There are remains of many castles, some of which are Baba Vida, one of the last Bulgarian strongholds during the Ottoman invasion and the Belogradchik fortress.