Liencres Natural Park is home to the the richest and widest area of sand dunes, shaped by sea and wind, along the whole stretch of the Cantabrian coast. Bounded by the Mogro estuary, it is the foremost protected area of Cantabria and extends over an area of 33.5 hectares. The Liencres beach, actually called Valdearenas, is the perfect setting for a stroll, starting off through the dense pine forests - planted to stop the dunes advancing - and then on to the dunes. The river Pas and the coastal currents are the main artists of these natural coastal sculptures, which, although off limits, provide a wonderful setting for the walk, increasing in size from small mounds to great hills after a few kilometres.

Care must be taken if you want to swim here as there is a steep slope and the waves and wind are strong and the currents dangerous. With the island of Conejera in the background, sunsets witnessed from the beach are unforgettable. Liencres is also a stopping off place for many migratory waterfowl including the plover, ringed plover and whimbrel, besides offering winter quarters for other species such as the cormorant, heron and yellow-legged gull.