The small municipality of Jasa lies hidden on the left bank of the Osia river, a tributary of the Aragón Subordán. Its limits are the Osia river to the west, the Sonal gully to the north, the Puyarron gully to the south and to the east the Luesia range, ascending to 1,500 metres before reaching the Cotin peak.

It is situated in the foothills of the Pyrenees among forests and old arable lands. The village itself is on a ledge overlooking the mouth of the Larrigo gully as it opens into the Osia river.

Jasa was a medium-sized village and royal dependency with 32 houses in 1495. Historically it was a part of the Aragües del Puerto valley and shared some territories with the latter. The local economy revolved around livestock and mountain agriculture which in the case of Jasa allowed it to benefit from the rich soils irrigated by the spring in the Estiva pass. The annual crop of wheat was turned into flour in the local mill at the foot of the village, next to the Larrigo gully. Until well into the 19th century, the surrounding hills were home to bears and wolves.

The parish church of Our Lady of the Assumption stands out in a village of traditional mountain architecture. Small barns, like the Sandiniés barn, are scattered around the municipality, illustrating the traditional style of architecture.

Its touristic resources emphasize the peacefulness of its streets and the walking routes available. There is a network of traditional paths and modern tracks that reach every corner of the municipality. Likewise, it is possible to reach the summit of the Luesia range by car on the Aisa road and enjoy the magnificent panoramic views.

Text taken from the Jacetania Area Signposting Plan. 2001-2006