Elevated view of the Dom Luís I Bridge crossing the River Douro in Porto, with iron arches spanning the water, red-tiled rooftops in the foreground, and hillside buildings under a clear blue sky. Porto is a city that reveals itself slowly, through wandering rather than rushing. It’s steep, a little scruffy in places, deeply atmospheric, and full of moments that sneak up on you – a burst of music drifting across the river, a sudden view over red...