Porto, Portugal

Porto gave Portugal its name — the Roman settlement of Portus Cale sat at the mouth of this river — and it has been a trading port ever since. The city that visitors walk today is largely eighteenth and nineteenth century, laid over a medieval street plan that survives in the lanes behind the Ribeira. Its landmarks are close together: the Clérigos tower, still one of the tallest things in the old city; the São Bento railway station, whose entrance hall is faced with twenty thousand painted tiles; the Livraria Lello with its double staircase; and the cathedral on the high ground, with a fourteenth-century cloister. The Dom Luís I bridge, built by a partner of Gustave Eiffel's firm and opened in 1886, is the image the city is known by, and walking the upper deck at dusk is the standard way to see the whole gorge. Across the water in Vila Nova de Gaia the lodges are open to visitors, and the flat-bottomed rabelo boats moored below the bank once carried the barrels down from the valley. A river cruise between the six bridges takes about an hour and is the easiest way to understand how the city is put together.