There are good stops along the route for a coffee and Melgaço has a really cool old town featuring a tower, open to the public.
The castle is the most prominent structure in town and is at the center of the old town. Open to the public the tower offer great views of town and the surrounding area. Its worth spending some time here as the old town, while small is quite picturesque. Another bonus is the restaurants in the area. Adega Sabino has a Cabrito de Monte that is fabulous!
Wikipedia:
The construction of the castle dates back to 1170 by order of the first King of Portugal Afonso Henriques (1112–1185). He granted a Foral charter to the town at the same time, encouraging the development of the town.
Afonso III (1248–1279) granted to the village in 1258 a second Foral Charter, promising privileges to the town.
In 1361 the traffic between Portugal and Galicia was required to pass through Melgaço demonstrating its importance at the time.