This city is located near the Basque border. It has an area of ​​96.7 km² and has 33,482 inhabitants. Castro Urdiales has an extensive bus line, which connects with the Basque city, which is only 35 km away.

The main monuments are located on a hill, such as the Gothic Church of Santa Maria, the Medieval Castle of Santa Ana and the Hermitage of Santa Ana.

It is the third most populous city in the Cantabrian community with just over 30 thousand inhabitants, with a magnificent history and many interesting places to visit.