Start from the car parking placed at the Col de la Pierre-St.Martin, near the french skiing station of Arette. From the ski resort you will have to drive about three km southwards, right to the spanish border. You can also reach the place from Spain, driving from Pamplona or Jaca to Isaba.
There is a wide space to leave the car on the eastern side of the road, just by a small (and usually closed) hut.
From the parking lot, start walking eastwards. There are two clearly visible paths by the road. Both are leading to our route, but the northern one is best and allows us to avoid some height loss. The first thirty minutes or so will take us round the pyramidal summit of Arlas (2021 m), standing in front of us. The path winds around its south face and leads to the Col du Pescamou. On the way, right at the southwest face of Arlas, there is the only water source you will find in the whole climb. Take good note of this and fill up your water bottles here if necessary.
Just south of Arlas stands the Col du Pescamou, overlooking some of the skilifts of the french ski resort of Arette. You will recognise the place because of this fact and because the border stone number 265 stands there. It's easy enough to go down to the french side and a couple of huts standing there might offer some shelter if you're lucky enough to find them open. But that is not our path. We have to go on the trail and reach in a further twenty minutes the Col de Baticotxe. There is another shelter over there, a tin one known as the "speleologists shelter".
Usually said to be closed, we found it open but does not seem to be properly cared for. The Col de Baticotxe is an important decision-making place. On a stone in this col you will find a red marking and arrow pointing east and saying "Anie". This is the beginning of the path leading to the Col d'Anies, on the GR-12 trail, and the Réfuge de Laberouat. Makes for a little longer walking but also leads to the summit of Auñamendi, being your first choice if in foul weather or if you see the slightest possibility of fog coming in. If you are lucky enough to enjoy a sunny day (just as we were), then you might prefer to go on all ahead. This second path, also marked by red paint and cairns, will lead you into the rocky karstic desert of the Arres d'Anie. Not a difficult walk, but it's not the place to get caught by fog or a storm. Just follow the marks of the trail for a trip up and down, hiking and scrambling, including some spots to do a little bit of pseudo-grade I climb. You will get in about 90 minutes to the base of Pic d'Anie.
In this spot it will become necessary to place your hands on the rocks to go up an easy corridor, but that will be the end of your trouble. At the top end there is a wide rocky terrace with stunning views over the karst and the southern peaks (from Midi d'Ossau to Orhi and including Mesa de los Tres Reyes, the highest peak in the spanish provinces of Navarra and Huesca. Only a twenty minutes walk up the south face of Pic d'Anie will be left, by easy scree slopes, first walking eastwards and turning left to get to the summit.
Snow and ice equipment for winter time. Walking poles would be useful in case you have to probe for the depth of potential snow bridges over the crevasses of the karst
GPS Waypoints for the Western Route (Karst de Larra)Col du Pescamou (Border milestone number 265):
42º 57'53'' N / 000º 44' 56'' W
Col de Baticotxe:
42º 57' 38'' N / 000º 44' 41'' W
Waypoints after Col de Baticotxe:
42º 57' 45'' N/ 000º 44' 54'' W
42º 57' 27'' N/ 000º 44' 32'' W
42º 57' 14'' N/ 000º 44' 26'' W
42º 57' 11'' N/ 000º 44' 23'' W
42º 57' 05'' N/ 000º 44' 12'' W
42º 57' 03'' N/ 000º 44' 00'' W
42º 56' 58'' N/ 000º 43' 47'' W
42º 56' 50'' N/ 000º 43' 46'' W
42º 56' 42'' N/ 000º 43' 30'' W
42º 56' 42'' N/ 000º 43' 22'' W