There are various maps which are useful to have when visiting Cantabria, especially by car.

Road Maps

There are various fold out road maps of Cantabria, two of the most useful of which are mentioned below, and one of which is certainly worth getting. 

Costa de Cantabria, Michelin, No. 143 Zoom España, 1:150.000, green, includes city plan of Santander, and information in English.

Cantabria & Asturias, Michelin, No. 572 Regional España, 1:250.000, orange, includes city plan of Santander and driving times.  

These are sold in most book shops, petrol stations and can also be found abroad (or ordered online at for example www.amazon.com).  At petrol stations larger Spain road atlases are also readily available.  Be aware that mapping in Spain is not as good as that in other countries, these two maps are very good, but from experience, there are still roads which do not appear, and other smaller ones which do...but actually don't exist or are just farm tracks (especially in higher, more remote areas).  In general they are accurate, but just be prepared for this!

Street Maps

The tourist office of every large town will have street maps available, usually for free.  They will also have maps of the local area, and often touring maps/guides too.  In some large towns and cities there are also street maps (called "callejeros" in Spanish)dotted around the main areas. 

Local Area Maps

There is a range of maps covering Cantabria (and the rest of Spain) available in some book shops and touristy shops (the largest selection is upstairs in the Estudio bookshop on Calle Vargas in Santander).  They are available in 1:50.000 (dark red), and 1:25.000 (either blue/red/white (newer version) or blue and white (older version)).  These are similar to UK OS Maps, though with less symbols. These are very useful maps if you are walking in the area.

Walking Maps of the Picos de Europa

If you are planning on going walking in the Picos de Europa, aside from the previously mentioned OS style maps, there are two maps which can be found in most touristy shops and book shops around the Picos.  These are most easily identified by their size, they are not the usual long thin type, but fatter, and their colour, one is yellow and one is green (they're usually found together).  They are both in both English and Spanish.

Picos de Europa and Oriental Coast of Asturias / y Costa Oriental de Asturias, Arados Ediciones, 1:80.000 (GREEN).  This map contains information on hostels, refuge huts, campsites, climbing schools, information centres, monuments, petrol stations etc., as well as 50 hiking trails around the wider area.

Picos de Europa Central and Eastern Massifs / Macizos Central y Oriental, Arados Ediciones, 1:25.000 (YELLOW).  This map is more detailed and contains information on hostels, refue huts, campsites and caves etc., as well as hiking trails in the Picos.

It is very useful to have both maps.