Senda del Arroyo (SO9), from the Paso de la Serrá to the Laguna Negra

The SO9 is the walking alternative to the tarmac track: it leaves the Paso de la Serrá car park and climbs 1.7 km, with 218 metres of ascent, among pines, ferns and beeches, crossing the streams on rustic bridges, to the upper car park, 200 metres from the lake. It is waymarked and has information panels. The Junta rates it as medium difficulty: it is short but steep and calls for mountain footwear. It is the way to go up when the upper car park is closed to cars.

What you will see

The path follows the stream that comes down from the Laguna Negra, within the park's great Scots pine forest, which according to Turismo de Castilla y León is part of the largest forested area in the Peninsula. The panels explain the forest and the water. At the end you reach the Laguna Negra, at about 1,800 metres, set beneath the cliffs of the glacial cirque, with a walkway and an improved path to go round it.

Deer, roe deer, wild boar and rock partridges live in the park; in silence and early in the morning, you may see one in the pine forest.

When and how

Allow about 45 minutes up and a little less down. It can be done all year except with snow or ice, when the slopes and the wooden bridges are slippery. In autumn, the beeches along the way change colour.

The starting point is the Paso de la Serrá car park. At Easter, on long weekends and in summer the Junta usually regulates access: cars stay at this car park, which is paid on those days, and you go up to the lake on the shuttle or on foot by this path. Outside those dates you can drive up to the upper car park and use the path only to come down, or the other way round. Confirm the year's dates and rates at the Casa del Parque.

With children

For children who already walk well, it is a short and entertaining climb, with bridges and water. With small children or a pushchair, the shuttle is more comfortable: you can go up on it and walk down, which is easier. Take a warm layer, because by the lake it is cool even if it is hot below.

To continue

From the lake leaves the Glacial Lakes Trail, the 13 km route to the Pico de Urbión. To understand the glacial landscape and ask about the paths, call in at the Casa del Parque, on the Vinuesa road. And for eating or sleeping nearby, see Los Ranchales or the Santa Inés rural hotel.