"One of the most famous sights in Germany, the Cologne Cathedral (known locally as the Kölner Dom) lives up to the hype. Its Gothic exterior, and especially its soaring twin spires, can be seen from all over the city, and its immense interior—measuring a whopping 66,370 square feet—brims with religious and cultural treasures. While its first stone was laid in 1248, the cathedral wasn’t finished until 1880. Today, its highlights include the Altar of the Patron Saints of Cologne by Stefan Lochner, the carved oak choir stalls, and the stained glass windows, which range from 13th-century examples to a more recent (and striking) addition by contemporary artist Gerhard Richter. The real treasure, however, is the Shrine of the Three Kings—an impressive work of medieval gold craftsmanship that’s bigger and grander than any other in Europe. Take it all in, then climb the 533 steps to the viewing platform on the south tower for a look over the city and, on a clear day, out to the Siebengebirge. Also be sure to visit the treasury, which holds artworks made from gold, silver, bronze, and ivory, as well as holy relics and sculptures from the Middle Ages."