Lac du Portillon

Lac du Portillon is a high-altitude lake tucked into the Central Pyrenees, within the commune of Oô in the Haute-Garonne department of southern France, right up against the Spanish border. Sitting at 2,580 meters above sea level and covering roughly 0.34 square kilometers, it ranks among the higher lakes in this part of the range and rewards only those willing to put in a full day of hiking to reach it.

Where exactly is the lake located?

The lake sits at the head of the Oô valley, well above the better-known lower lakes of Oô and Espingo. Its coordinates, 42.7008, 0.5089, place it deep inside a ring of rocky ridgelines that mark the frontier between France and Spain. The surrounding terrain is stark: bare slopes, glacial moraine, and granite outcrops typical of the high Pyrenean landscape.

How do you get to Lac du Portillon?

Hikers usually start from the Granges d'Astau car park, reached by road from Bagnères-de-Luchon along the valley leading toward Oô. From there the path first climbs to Lac d'Oô, a lake famous for the waterfall that feeds it from the slopes above. The route then continues along the GR10 long-distance trail and yellow waymarks 42/43 up to Lac d'Espingo, passes Lac de Saoussat, and finally reaches the dam that impounds Lac du Portillon.

How long does the hike take?

The stretch from the car park up to the area around the Espingo pass typically takes about two hours. Covering the remaining distance to the lake and its refuge adds roughly another two and a half hours. In total, this makes for a demanding full-day outing that calls for solid fitness and sturdy hiking boots, since the final section crosses rocky, uneven ground.

Is there anywhere to stay overnight near the lake?

Yes. A mountain refuge stands right beside the dam, run by the French alpine club. It offers around 25 beds spread across a handful of small rooms and two larger shared dormitories. The hut serves as a popular base for hikers pushing on toward the higher ridges near the border, and booking ahead is advisable outside the quiet winter months given the limited number of beds.

What should visitors know before setting out?

The lake occupies a natural basin that was later enlarged with a hydroelectric dam, which explains the noticeably straight, engineered edge of the shoreline near the barrage. The approach crosses protected mountain terrain, so park rules on camping and waste apply along the way. Hikers should carry enough water and windproof layers, since temperatures above the treeline can drop sharply even in midsummer.

FAQ

How high up is Lac du Portillon? The lake sits at 2,580 meters above sea level, deep in the high-altitude zone of the Central Pyrenees.

How large is the lake? Its surface area covers approximately 0.34 square kilometers.

Where's the best place to start the hike? Most hikers begin at the Granges d'Astau car park, accessible by road from Bagnères-de-Luchon.

Is the trail suitable for beginners? Given its length, several hours of steady climbing, and the altitude involved, the route is better suited to hikers with some mountain experience and good fitness.

Can you stay overnight near the lake? Yes, a staffed mountain refuge sits right next to the dam, offering several dozen beds and serving as a stopover for those continuing toward the Spanish border.

Is the lake natural? It began as a natural basin that was later expanded with a hydroelectric dam, which is why part of its shoreline looks distinctly man-made.