Close to Loarre Castle, access is via very good mountain bike and gravel tracks.
A very well kept free shelter with a fireplace, a long table and even cooking utensils.
It does not have a bed.

Refugio semi cerrado, elevado del suelo, al lado de un río en un área recreativa tranquila. Hay un grifo con agua y un enchufe (no sé si el enchufe funciona).  También hay un cobertizo grande a pocos metros y zona para hacer fogata en la que veo que suelen dejar leña.

43.237311,-8.088636

About 12km from Biel is this shelter right on the slopes, with easy access for gravel and mountain bike.
It has a picnic area outside and a fireplace inside and a large table to eat (I slept at the
table).
It has a second loft-style floor with more space to sleep.
Quite clean.

In the Barranco de la Hoz, going up from Vallada towards Ayora, in the heart of the Enguera mountain range, there is this small shelter, a little off the track but very close to it and well signposted. The times I have been there, it is in perfect condition and clean enough to spend a night inside.

At the entrance to the village of Nocito there is a pergola with an informative sign.
Perfect place to sleep when the weather is nice.
It has no walls, but it does have a roof.
There are some pools nearby, and the village is 200m away.

Very close to Àger is this hermitage, far from any urban centre, with a roof and three walls.
It faces south, so it is well protected from the wind in winter.

Guaso is a very small village and this place is on the hill, next to the church. A place where no one is bothered.
Incredible views of the Peña Montañesa.

Wikipedia:
Above the town of Guaso, there is a church and an old conjuring place, from which the priest and the population invoked to divert or undo storms or thunderstorms that could ruin the fields and crops.

Arriba del puerto de Santa Bárbara está esta ermita perfecta para dormir al cobijo de lluvia o viento, con 3 paredes y un techo. Bastante amplia como para poder alojar a 6 ciclistas.
Afuera hay mesas de pic-nic y una fuente.

In Rondane National Park you pass a place full of private cabins. This cabin has an open bathroom next to it, where you can lie down comfortably for a nap and wash your face.
Leave it as you found it!