Starting as a Roman fortified tower built to watch of the crossing of two Roman roads, For much of its history, Luxembourg’s capital was best known as a fortress, which was passed between the European powers, each of whom reinforced and expanded its fortifications. By the 19th century, Luxembourg City was perhaps the mightiest fortress in the world, and was so desirable it almost caused a war between the Netherlands and Prussia. Today, visitors can walk through the picturesque Old Town, where, along with historic buildings like the beautiful Ducal Palace, you’ll find a surfeit of strange spaces, such as the Alzette gorge’s labyrinth of military tunnels, which now offer stupendous views over the town center.