The Río Martín runs northward through a series of deep gorges before reaching the Ebro, and the villages along it are among the least visited in Aragon. Cueva del Garroso is one of the painted sites in this valley, in the cultural park that protects the rock art of the region, and it forms part of the UNESCO listing of Levantine art in the Mediterranean basin. The cave is a modest opening in a limestone cliff, and the paintings inside are small, in red, and faint in places.
The nearest town of any size is Andorra, in Teruel province, a place built on coal. For decades the open-cast mines and the power station dominated the area, and the town still has a plain industrial feel, though the surrounding country is gentler than that suggests. Olive groves stretch across the terraces, and the oil from the Bajo Aragón has a protected name. Alacón and Oliete are small villages with about four hundred and fifty inhabitants each, and between them they have a few bars and a church or two.
I like the Bajo Aragón for its silence. Roads run along the river and cross high plateaus where the only sounds are the wind and the larks. The bends are open, the surface is mostly good, and the traffic is light. There are long straights where the wind can catch a bike, so keep a firm grip. In the gorge itself the road narrows and the cliffs close in.
Fuel is available in Andorra, about twenty kilometres away, and it is worth filling the tank there. Cafes in the villages open early, and a coffee and a slice of tortilla make a good start to the day.
Spring and autumn are the best seasons. The summer sun is harsh, and the winter nights are cold. The walk to the shelter is a short but rough one, and the area is protected, so follow any signs and ask locally.