From Laruns, take the D934 towards the Col du Pourtalet to Gabas and then to the southern end of Lake Fabrèges. Turn left onto the D431 and head north to the upper car park at Fabrèges. From there, the Sagette cable cars take you to the Artouste resort, where you will find the lower station of the small train, one of the highest in Europe, which you will need to take to the upper station, the starting point of the hike.
(S/E) From the upper station, take the marked trail to Lac d'Artouste to the south-west. The trail climbs rapidly and joins a marked intersection before a bridge.
(1) Do not cross the bridge, leave the path to the Lac d'Artouste dam on your left and take the path to the Refuge and Lac d'Arrémoulit on the right at the sign.
Follow this trail around Lake Artouste on the right, along its left bank to its southern end.
(2) Then climb up the winding path until you reach a small lake crossed by the Gave de Soussouéou stream, then join the Lac d'Arrémoulit dam, ignoring the paths that branch off to the right towards the Col d'Arrious and then the Orteig pass at the two intersections you encounter on this climb.
Walk a few metres to the left on the small dam of the large Lac d'Arrémoulit, cross the small wooden bridge over the stream of the previous mountain stream and then reach the Refuge d'Arrémoulit.
See Practical Information.
The Lac d'Arrémoulit is absolutely splendid. On its opposite shore, you can see the Pic d'Arriel and the Petit Arriel (pointed peak). Once at the refuge, locate the pass in the south-east direction.
(3) Take the path that leaves from the refuge, marked by cairns to the south-east: this path is not shown on the IGN map but is clearly marked on OSM. Start by going around the large Lake Arrémoulit on the left, following part of its right bank. Then proceed from cairn to cairn until you go around a small lake on the left.
After veering slightly away from the large Lac d'Arrémoulit, the trail rejoins its eastern side. From there, climb south-east through the scree, following the cairns, then reach the Col d'Arrémoulit.
(4) After a contemplative break on the French and Spanish slopes, retrace your steps to the top station of the little train (S/E).