Metz is a city in northeast France at the confluence of the Moselle and the Seille rivers, near the junction of France, Germany, and Luxembourg. Metz has a rich 3,000-year-history. It was a Celtic oppidum, a Gallo-Roman city, the Merovingian capital of Austrasia, the birthplace of the Carolingian dynasty, and is one of the oldest republics in Europe. The city is steeped in Romance culture, but strongly influenced by Germanic culture due to its location and history. Noteworthy buildings include the Gothic Saint-Stephen Cathedral with its largest expanse of stained-glass windows in the world, the Basilica of Saint-Pierre-aux-Nonnains, the oldest church in France, its Imperial Station Palace with the apartment of the German Kaiser, and its Opera House, the oldest one working in France.