Overnight in Lisbon, Portugal’s lively capital, where winding streets lead to historic cathedrals and grand plazas. Sail roundtrip from Porto and cruise the Douro River Valley, the world’s oldest demarcated wine region and a UNESCO Site, where rural quintas line the hillsides. In Spain, visit Salamanca, home to one of Iberia’s oldest universities, before returning to Porto to enjoy its namesake wine, flavorful food and evenings of soulful fadó music.