so many!!!! If you like biggish cities, obviously Avilés, Gijón or Santander.
If you want just a quiet bucolic place with not much on it, by the seaside, this would be a list of my favourite places
Zarautz
Laredo
Buelna
Ribadesella (try kayaking in the river, it is BEAUTIFUL)
Luarca
and, for...