In the remote northern region of Trás-os-Montes, Chaves (meaning ‘keys’) is only 10 km away from Spain and lies on the upper stretch of the river Tâmega. It is a spa town steeped in history, the most important example of which is the fantastically maintained Roman Bridge. This feat of engineering was completed at the end of the 1st century and all twelve arches are still visible. Reputedly built…