ApproachStart from Balneario de Panticosa, in the spanish Pyrenees (province of Huesca). Walk around the lake (Ibón de Baños) to its northern side, right by the buildings, and then turn west to follow the lake banks. In the western end of the lake there is a bridge over the river. From this point on, you have two options to meet the Garmo Negro path. The easiest one is to complete the tour of the lake. In the corner placed across the lake from the resort buildings there is a clear path that winds across the forest and starts the climb.
The first section of the climb winds across the forest, not too steeply, in search of the prairies of Mallata Baja de Argualas. It's just a matter of looking where you put your feet. Good trail and no chances of missing it -even in foul weather-. You will have to follow it for some 45 minutes until it turns definitely north in search of the Ibón de Arnales. The first section of the climb comes up through the forest, then comes out to an extense prairie (Mallata Baja de Argualas) and finally turns right (north) across a small barrier of pine trees. Just after crossing this barrier, there is a small path starting on your left. It is the path to the Cuello de Pondiellos (Pondiellos Col), marked in a stone by the words "Garmo Negro".
At this point the path turns left and faces the peaks, going on up through pastures to find a small rocky step. This is crossed by the path without any need for technical climbing, just walking, and afterwards you will find yourself in the Mallata Alta de Argualas. This is an extense area of pastures placed just under Garmo Negro, which is the huge pyramid standing in front of you. Watch out for the correct route in this point: on your right (north), there is a huge scree and rock slope leading upwards to the Cuello de Pondiellos. Some cairns mark a path through it, but this is the path to the Cuello de Pondiellos and Picos del Infierno (see link). Our route to Garmo Negro goes left, walking around this rocky chaos in search of a small couloir. That is the key point to get higher. Other possibilities would also take you to the summit, but this is the shorter one. Walk up the couloir looking well where you put your feet, there might be some free rocks. Otherwise, it's not dangerous. When the couloir widens, start looking for the exit on your left. It leads to a grassy slope and might be marked by a cairn. That's the beginning of the path to the Collado de Argualas, a small col in front of you (just a little bit to the right). At first the path goes through grassy terrain and as it climbs towards the col gets into rocky and scree areas. No real difficulties, but you might find some snow as you approach the col (even in summer season). After crossing the col you will find yourself in a small hollow area placed between the peaks of Argualas (on your left), Algas (left, a little bit to your front) and Garmo Negro (right). The only thing left shall be to reach the (at last!) obvious summit. I would advise not to go straight for it: the gravel slope can be quite slippery and uncomfortable to walk on. Better go ahead for the last ridge and climb to your right afterwards.