This is a lovely run around two interior parks: Parque Atlántico de Las Llamas and Parque Doctor Mesones, with an optional add-on of the waterfront Parque Mataleñas. Nice variety and totally off road!
Short Loop: 4.6 km. The route starts at the parking lot of Parque Atlántico de Las Llamas, a more modern park with paths around reedy marshland lakes (there’s an outdoor gym at the south end). A loop is ~2.6 km, with additional paths for more. Then head east on a cycle path alongside the stadium & sports complex. It’s 0.7 km to the Parque Doctor Mesones, with a nice 0.5 km loop around the path there.
Long Loop: 8.9 km. This adds a 4.3 km out and back along the beautiful clifftop path of the Parque Mataleñas. There are great view of the water and beach below, and several designated viewpoints (mirador).
Add-Ons: A grassy path leads further north to Parque Cabo Mayor, another beautiful clifftop park with great views.Can add even more with out Santander Waterfront route.