This is not a difficult route. It can be split in two different parts, both of them on grassy terrain. The first half goes from the Lizara Hut to the Collado del Bozo following a good path, on a grassy slope without any real problems unless it's covered by snow. After the col, the terrain is still easy and grassy but the path disappears and you will have to walk along an easy ridge with rather steep slopes on both sides (specially on the east side). This could give some trouble to unexperienced hikers, but no experienced hikes should have real problems.
In winter time, this route offers good terrain to practice your winter technique. BUT... be extremely careful, carry the proper gear (clothing, ice axe, crampons), get all available info on avalanche risk and get yourself an experienced partner if you have the slightest doubt about your abilities. Remember, turning back is never a failure, it's just sensible behaviour.
To approach the Lizara Hut by car, start from Huesca or Pamplona, in northern Spain. From any one of both towns, follow road N-240 towards the other one. At Puente la Reina (88 km away from Pamplona, or 72 km away from Huesca) you will have to turn north by road A176. This is the road running alongside the river Aragón Subordán, entering the Valley of Hecho. After 16 km, turn right once again to take road HU212 into the valley of Aragüés. This is a narrow and not-too-good road that will take you to the village of Aragüés del Puerto. Keep going after the village, in 7 km more you will find the Restaurant "Los Corralones" (in a beautiful pine forest), and 3 km farther the parking of the Lizara Mountain Hut, at the base of Bisaurín.
Closest train stations: Jaca (33 km)
Closest airports: Huesca (96 km), Pamplona (116 km), Zaragoza (165 km)
Route DescriptionThe full route is (in clear weather, of course!) within sight of the Lizara Hut.
Start walking north from the parking lot in front of the hut, along the lower area within sight and avoiding the slopes on your left (those ones lead towards the Collado del Foratón and Bisaurín). You will enter a small plain area (Plana de Lizara) under the southern cliffs of Bisaurín and the west face of Bernera. It's not hard to find cows up there in summer time. Turn right (east) along the plain and start walking uphill slightly to your right (that is, south/southeast) at its further end. The path is clearly seen when not covered by snow, and it will take you soon to the small shelter of the Caseta de Napazal.
After the Caseta de Napazal, the path turns eastwards and climbs the wide grassy slope of the mountain in search of a gap between the cliffs of Sierra Bernera (on your left) and a lower hill. That gap is the Collado del Bozo, access to the upper valley of Aisa and to one of the routes of the Llana del Bozo. When you reach the col, it will only be a matter of turning south and following the wide ridge to reach the summit of Mesola. Before that, you will also be able to step on three smaller summits: in the first place Punta del Cuello del Bozo (2083 m), after that Punta de Napazal (2128 m) and finally Punta Petrito (2177 m)
In good weather, without any snow on the mountain, there are no special needs. Good boots and a backpack with (just in case) food, water and some warm clothing should be enough. Walking poles could also be useful for the way down.
In winter time, snow can turn the easiest climb into a trap. Therefore, no climb to Mesola should be attempted unless you have the proper (thermal, waterproof, windproof) clothing and full winter gear (including gaiters, crampons and ice axe). If you have any doubt about your equipment of about your ability to use it, get yourself an experienced partner or place your upper limit at the Collado del Bozo. Think safe, the summit will always be there for a summer attempt if winter conditions are above your abilities.