From a Roman military outpost, Strasbourg has grown into one of the most beautiful and important European cities. Known as one of the four de facto capitals of the European Union, it was the first city in the world to have an entire district classified as a UNESCO World Heritage Site. Petit France, accessed by crossing a 14th century fortified bridge, is filled with charming half-timbered houses dating back to the 1500s. Criss-crossed by waterways, weirs, and locks, this lost-in-time district is also a great place to sample classic Alsatian fare like tarte flambée. Strasbourg’s standout monument is its towering sandstone cathedral. Begun in the 12th century in the Romanesque style, it evolved into one of the most spectacular examples of Gothic architecture - not to mention holding the title of tallest building in the world until 1874. From the impossibly delicate facade to the monumental organ played by Mozart, every aspect of the cathedral is sublime.