It is 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.

[2] By 1404, it was emerging as the main town of the region and was organised into seven Hermandades, military units aimed at retaining law and order.

In 1497, Prince John, son of Queen Isabella I of Castile and King Ferdinand II of Aragon met his affianced wife Margaret of Austria here, the meeting or marriage ceremony probably taking place in La Casa de las Princesas.

These works contributed to an economic boom in the region and the town becomes a bustling and prosperous place, on one of the main routes to the port of Santander.

[5] This is one of the largest reservoirs in northern Spain and is mainly filled in spring as a result of the melting of the winter snow in the mountains.