The International Bridge connecting Tui to Valença do Minho on the Portuguese side is one of the more beautiful bridges on the Iberian peninsula — an iron lattice structure from the late 19th century that spans the River Miño at the point where it marks the border between Spain and Portugal.
Walking across the bridge takes about five minutes and costs nothing. The views from the middle — upstream toward the mountains, downstream toward the Atlantic — are excellent. On the Portuguese side, the walled town of Valença is worth exploring: a 17th-century Vauban-style fortification with bastions, moats, and a town of shops selling linen, ceramics, and wine. The combination of Tui and Valença makes for a good half-day on the border.