Santander is a seaside capital that happens to have a mountain range at its back. The city wraps around a broad, sheltered bay, with long beaches at El Sardinero on the Atlantic side and a working harbour facing the old town, and on a clear day the Picos de Europa show as a faint white line far to the west. A great fire in 1941 destroyed much of the historic centre, so the architecture is mostly post-war, but the waterfront has been given a bright new face, with the glass and steel Centro Botín by Renzo Piano projecting out over the water. For riders arriving from England, the ferries from Plymouth and Portsmouth land here, which gives it a slightly salty, expectant air.
Eat before you leave. Anchovies from the Cantabrian Sea are the local pride, along with rabas, crisp fried squid rings, and sobaos pasiegos, the soft butter cakes that come from the valleys inland. The Palacio de la Magdalena, a royal summer residence of the early twentieth century, stands on a headland with gardens and a long view across the bay, and is worth a stroll if you are in no hurry.
The day's riding goes inland and south, toward Puente Viesgo and the caves of Monte Castillo, where early humans painted the walls tens of thousands of years ago. The caves of El Castillo and Las Monedas sit within the same limestone hill, part of the UNESCO listing for Cantabrian cave art. The roads between Santander and the Pas valley are generally smooth and quick, with gentle curves through green meadows and eucalyptus, and then narrower and more rural once you leave the main road. Cantabria is famously rainy, so the hills are a rich, damp green and the roads can be slick in the morning. Visits to the caves are limited and usually need advance booking, so check before you arrive and carry something to put over your riding jacket in the cool of the cave.
Fuel is no concern in a city of nearly two hundred thousand, and there are stations on the ring road and around the port. Bring a waterproof layer whatever the forecast says. The weather on this coast rolls in from the sea, and a bright morning can be grey by lunchtime.