Silesia is a historical region of Central Europe that lies mostly within Poland, with small parts in the Czech Republic and Germany. Its area is approximately 40,000 km2 (15,400 sq mi), and the population is estimated at 8,000,000. Silesia is split into two main subregions, Lower Silesia in the west and Upper Silesia in the east. Silesia has a diverse culture, including architecture, costumes, cuisine, traditions, and the Silesian language. The largest city of the region is Wrocław.

The Oder is a river in Central Europe. It is Poland's second-longest river in total length and third-longest within its borders after the Vistula and Warta. The Oder rises in the Czech Republic and flows 742 kilometres (461 mi) through western Poland, later forming 187 kilometres (116 mi) of the border between Poland and Germany as part of the Oder–Neisse line. The river ultimately flows into the Szczecin Lagoon north of Szczecin and then into three branches that empty into the Bay of Pomerania of the Baltic Sea.