Cerro Merino-Cascada del Purgatorio roundtrip 7 km

This roundtrip is challenging through a wild environment on tracks which are sometimes hard to discern, and require scrambling and orientation skills. The paths are on openstreetmap.org, but in the field hard to find and you sometimes have to find your own way. Part of the track is through pine forest and some on rocky and grassy slopes. The hike takes you down to the Arroyo de Aguilón river, and to the waterfall Cascada de Purgatorio. The trip is in the Parque Nacional de la Sierra de Guadarrama. The start is at a parking along the road Carretera de Rascafria. There are no facilities on the way, and I did not see anybody, apart from some cows and a red deer. The rivers may dry up in the dry season, but during my trip in April there was more than enough water, and waterproof shoes were required. High grass and bushes should discourage you to wear shorts on part of the route.
From the parking you follow a minor track through the pine forest. This is an easy part with little growth beneath the trees, and although you do not see much of a path, your progress is good, and descent only minor. After some time you get to an open space with views of the mountains. After this, the descent is steeper, and you follow a clearing between trees which is now full with broom bushes. After some time you need to leave the area with brooms and get onto a rocky and grass slope. From here you steeply descend towards the river, and progress is slow. When you get down to the river you get onto Ruta 199, a better discernible path. You follow the river downstream a short stretch, and then have to go up and down around the Cascadas del Arroyo Aguilón. There is a bit of scrambling on scree involved. You get down to the river again and follow it for a while. Again the path ascends away from the river, and the path bifurcates. You go down to the river again, and cross a smaller stream through a side valley. From here, you ascend again across a rocky elevation. On the way the views are good of a waterfall looking back. On the top (55 m ascent) the views towards the Rio Lozoya valley are good. You descend again quite steeply on a clear but small path to the bottom of the valley of the Arroya Aguilón. Here there is large and more popular path coming from El Paular. You follow it upstream close to the river to a viewpoint of the Cascada del Purgatorio. From here you take the same way back to the top of the rocky elevation above the waterfall. Here you take a minor path more south east of the path you ascended on. This minor path takes you to the bottom of the aforementioned side valley and you cross the stream again. A bit further up is a path which takes you upstream along the bottom of the valley. At a certain point you leave the stream and ascend quite steeply through the pine forest. Here, the track is difficult to see again, but again there is no undergrowth so you can choose your route quite easily. The path takes you all the way up the slope to a larger former forest track. You follow this track with broom bushes a bit further up to the Cerro Merino and you descend the last stretch back to the parking.