Boo de Pielagos

Boo de Piélagos is a locality in the municipality of Piélagos, in Cantabria, situated at the mouth of the Pas river where it enters the Bay of Biscay through a broad estuary. The Pas estuary forms a significant tidal wetland system, with salt marshes, tidal channels, and the shallow lagoon of Liencres protecting the inner coastal terrain.

The Dunes of Liencres Natural Park, adjacent to the Boo area, preserves one of the best-developed Atlantic dune systems on the Cantabrian coast, with extensive marram grass dune fields and the coastal pine forest that stabilises the dune edge.

For pilgrims on the Camino del Norte, the Pas estuary at Boo represents another estuarine crossing, with the route threading through the protected dune and marsh landscape of the Liencres park on the approach toward Santillana del Mar.