The Picos de Europa National Park offers visitors a free guided tour service, accompanied by interpretive guides. Every year, from the 1 from July to the 30 from September, in the four main accesses to the National Park (Lakes of Covadonga, Cabrales, Liébana and Sajambre-Valdeón) a daily route is carried out, except in the area of Lagos de Covadonga, which takes place from Monday to Friday.
To participate, the only requirement is to be at the starting point at the indicated start time. The maximum number of people for each route is 25, as long as they come individually or in small groups. No advance reservations are made nor are numerous organized groups allowed. Attached link to pdf in which the routes that are carried out in each area are indicated every day of the week.
The organized groups also have an accompaniment service that runs from March to November, both in the Asturian, Cantabrian, and Leon part of the National Park. School groups have added services such as environmental education activities.
More info with detailed routes National Parks