There are lots of walking possibilities in Añisclo. First time, I went with Club Peña Guara and visited the caves and the Ermita San Urbez.
Later, R and I did Los Sestrales. This turned out to be much longer and harder than we'd expected. The route is fairly well marked from San Urbez, and at first is easy path. Later there is a grotty bit of scree and some scrambley moves to gain the wide flat area above - Los Sestrales Bajos & Altos.
The views that day were super-impresionante.
Later I climbed Pico Mondoto on the other side of the Cañon, where the views are equally spectacular.