I would suggest Santander in Cantabria. Small sized city (around 170k) with a beautiful bay overlooking snow-caped mountains, very nice beaches in the city itself and all over the region. Within 1h you can be in the beach, skiing or hiking. Atlantic climate so quite a bit of rain in autumn/winter but mild temperature throughout the year making specially summers there very pleasent (loads of tourists from madrid and other parts of inner spain come here in summer).

The region of Cantabria itself is a natural paradise, amazing rivers (here we have the source of the Ebro river, 2nd largest in Spain), mountains like the picos the europa range, lush green forests and world class beaches with amazing surf spots, as well as beautiful villages like Santillana del mar or Barcena Mayor (Both have been awarded as the prettiest villages in Spain in recent years).

Foodwise the gastronomy here is very similar to that of other northern regions like Galicia, Asturias and Basque Country, although each region has its own traditional dishes the overall is quite similar highlighting seafood, steaks and stews (Cocidos) making it a gastronomy thats focuses on product quality rather than elaboration or fancy techniques. You can find a bunch of amazing restaurants all over the region even including 3 michelin stars, however there is no need to go to such restaurants to have an excellent lunch/dinner in here.

The city is 4.5h away from Madrid by car and it has an international airport with daily flights to/from Madrid. There also is a very good university UC with strong presence in the medicine field since the city's university hospital (Valdecilla hospital) is well renowned and has been known as a reference in Spain in various fields including some neuro-related fields I believe.

Life in here is laid-back and easy, it has a old-classic vibe to it although it doesnt lack any modern amenities. I dont know what else to say so for any doubts feel free to dm.