Rouen

This port on the Seine was an important city through the Middle Ages. Among its sights: hundreds of medieval half-timbered houses, a remnant of the castle where Joan of Arc was tried for heresy and the Gros Horloge (Great Clock) housed in a 14th-century Gothic belfry. The clock kept time for 5 million hours without stopping once. The embalmed heart of Richard the Lionheart was buried (and later exhumed) in the city's Cathedral of Notre-Dame, also called Rouen Cathedral.