3 - 4
FATMAP difficulty grade
##Ascent The start takes place a few hectometres after the village of Puertolas, at the level of a small pass where the road splits (on the left for Bestué, on the right for Escuain).
The route initially follows the ridge line towards the N.
Then it gradually slows towards the W, leaving the ridge, to go to the S side of the Castillo Mayor.
At about 1500 m, pass the large lock that gives access to the upper basin, reach it at 1750 m.
From there, either climb directly to the N towards the top (karst terrain), or pull further to the right to reach the top by the ridge. ##Descending By the same route.<br/><br/>_This Adventure has been shared under the [Creative Commons Share Alike](https://creativecommons.org/licenses/by-sa/2.5/) licence._