Roman Bridge, Colloto, Siero

This bridge has specific proof of its Roman origins - though that´s a two-edged sword: the proof is in the form of  a "treasure" of Roman coins found in the main arch of the bridge. The other edge is that the treasure was found when the bridge was seriously damaged in the Spanish Civil War. The present-day bridge, then, has Roman origins, almost certainly substantially augmented in the medieval period, and a twentieth-century partial reconstruction. 
The bridge spans the Rio Nora, which rises in Sariego and flows into the River Nalon. It forms part of the Camino de los Santuarios - the Trail of the Sanctuaries - which atb 220 km long, incorporates the Cathedral of Oviedo, the Sanctuary of Covadonga, and the ancient church of San Torbio in Liébana in Cantabria. There´s apparently historical provenance for that route, though I think it´s recently been resurrected by some Tourist Board or other...