Copenhagen, Denmark. The city owes much of its charm to the buildings erected by Denmark’s monarchs, and boasts a treasure trove of late-Renaissance and Rococo architecture and is known as the Venice of the North. See the fabled statue of Hans Christian Andersen’s Little Mermaid, a symbol of the city. Stroll along the old harbor of Nyhavn, lined with cafés, restaurants, and 500-year-old gabled houses.