The Las Dunas de Liencres National Park is located between the Liencres coast and the Mogro river (a tributary of the Pas river). It covers 194ha and consists of beaches and dunes. Due to strong winds that affect the area the dunes constantly move and are re-sculpted making it one of the largest dune areas in Cantabria.
The Las Dunas de Liencres National Park is home to a sizeable amount of lizards, snakes, vipers and amphibians, such as the midwife toad, and the three varieties of newt existing in the region. The reserve is used by many birds during migration, particularly the ringed plover, dunlin, grey plover and whimbrel.
The majority of the dunes, some measuring up to 40 metres in height, were replanted with marine pine trees some decades ago.