 The municipality, one of the smallest by land area in Cantabria, is notable for being one of the nearest towns to the headwaters of the Ebro River.It is completely surrounded by the municipality of Campoo de Enmedio and was created a city by King Alfonso XIII in 1927, being one of only three urban centres in Cantabria with that honour, the others being Santander and Torrelavega.The first documents mentioning the town date back to the year 1000, when it was divided into four solars by Sancho García, the Count of Castile.