Frías is a town located in the northern part of the province of Burgos. In 2010 it had a population of only 275 inhabitants.Frías is a historic medieval town on a hill above the river Ebro. Now a popular tourist spot it has an impressive castle dominating the river and the twelfth century bridge across it. It is considered to be the smallest "city" in Spain, having been given that title in 1435.The castle of Frías is a mixture of buildings of XII, XIII, XV & XVI centuries. Probably the most impresionant rock castle at northern Castile, it was adquired by the Crown in 1202. In 1446 king Juan II left it to Pedro Fernández de Velasco, comstable of Castile & Duke of Frías