Catedral de Santa Maria dominates Tui's old town from a high position above the Minho, looking almost as much like a fortress as a church. The Romanesque core gives it weight, while the Gothic west portal adds the finer carving that draws most visitors in close.
It is the natural focus of a walk through Tui, especially if you are following the Portuguese Camino or crossing between Galicia and northern Portugal. Step inside for the cloister and treasury if open, then come back out for the views and stone lanes around the cathedral hill.