I will be renting a car for 6 days in late June and driving between San Sebastian, Santander/Picos de Europa and Santiago. I have no idea how long I will want to stay in each area. Do I need to book hotels beforehand or can I just improvise and not worry about finding space in hotels at the last minute? Thanks for your advice!

Besides trying to cover a lot of country in only 6 days, I'd suggest booking ahead instead of wasting your valuable time trying to find somewhere to stay each night and ending up with what's available.

Look at www.maribelsguides.com for lots of helpful information.

A help to plan your travel:

*San Sebastian
http://www.donostia.org/CAT/Home.nsf...N?OpenFrameset

*Picos de Europa
http://www.asturiaspicosdeeuropa.com/

*Asturias
http://www.infoasturias.com/action/I...metodo=entrada

In late June you shouldn't have too much problem with places to stay, but I think it's also prudent to book ahead. In Santander, I would head for Sardinero; parking will be easier. We stayed at Hostal Paris. In Potes (Liebana) we stayed at Hostal Picos de Europa.

You left Bilbao and Santillana del mar out of your proposed itinerary ...

I might add the Rioja area to this trip but take care you have a lot of traveling and some roads really do twist and turn.

I guess it is obvious but the Picos may get in the way a bit . you really do have to drive around them

Thanks everyone for your great insights and information! Please keep them coming.

kauf-- don't book hotels if this is a 6-days road trip in Northern Spain. There are tons of rural inns and hotels by the roadside in Northern Spain. At about 4-5pm, etc...start narrowing down a destination and take with you a good guidebook and Michelin maps. There is always a major city within driving distance. It will not take you a lot of time to narrow down lodging. Check http://www.turismo-rural.com/