In Spain aside from Spanish we have other 3 languages. Gallego, Catalán y Vasco the last one it is used in pais vasco and is very difficult to understand for the rest of the spanish, and even for the vasque people themselves.

Galician it´s widely talk in Galicia specially in rural areas and have a lot of similitudes with Portuguese. Galicia is the spanish region at the top east of the map just above Portugal.

The catalan and some differently named but scencially identicall languages it´s used in Catalonia, Mallorca, Valencia and other areas.

In fact almost everybody that speaks this other languages understand and it´s able to use spanish, but they don´t always want. If you speak spanish you won´t have any problem to find people to talk with you in Spanish in these regions (Cataluña, Galicia, Pais Vasco) specially if you are not spanish.