With rich cultural attractions and world-class museums, the compact city of Porto spreads upward from both sides of the Douro River, making it easy to explore on foot with a vigorous hike. A UNESCO World Heritage site, the historic Ribeira quarter on the waterfront is a maze of cobblestone streets and picturesque squares that tell a 2,000-year history in architecture. Dating to the 12th century, Porto’s Romanesque cathedral has evolved with a Baroque loggia and Gothic cloisters, while the neoclassical Palácio da Bolsa and the Beaux-Arts-style railway station bring the city into the 20th century. Cross the Dom Luís I Bridge, also a UNESCO World Heritage site, to visit local wine cellars and taste the region’s famous port wine. Further inland, medieval castles meld with 15th-century palaces in yet another UNESCO site, the first Portuguese capital of Guimarães.