A small ferry runs across the Minho river from the Caminha quay to A Guarda in Spanish Galicia. The crossing takes about ten minutes and the boat is just big enough for a handful of cars and a few foot passengers. It is one of the more pleasant border crossings in Europe — no formalities, two countries within sight of each other, the river wide and quiet.
A Guarda on the Spanish side is worth the trip in itself: a fishing port famous for spider crab, with the Iron Age Castro de Santa Trega rising above it on a wooded hill. Ferries run roughly hourly during daylight in summer and less frequently the rest of the year — check the local timetable, which changes seasonally. Coming back in the evening on the last ferry, with the lights of Caminha just coming on, is exactly the kind of thing that makes the town memorable.