Poznan (; , known also by other historical names) is a city on the Warta river in west-central Poland, in Greater Poland region. It is best known for its renaissance old town, destroyed during World War II and then rebuilt, and Ostrów Tumski cathedral. After the second partition of Poland Poznan was administrated by Prussia, and then, with the unification of Germany after the Franco-Prussian War of 1871, the province of Posen became part of the German Empire. Furthermore, the city of Posen was officially named an imperial residence city, leading to the construction of the Imperial Castle, the Imperial District, the Opera House, new city walls, railway station and many other sites which make a big part of its landmarks to this day. Today, Poznan is an important cultural and business centre and one of Poland's most populous regions with many regional customs such as Jarmark Swietojanski, traditional Saint Martin's croissants and a local dialect.