Regen (river)
 The Regen (Czech: Řezná) is a river in Bavaria Germany and a left tributary of the Danube at Regensburg Germany. The source of its main headstream the Großer Regen (Big Regen) is located in the Bohemian Forest on the territory of the Czech Republic near Železná Ruda. The river crosses the border after a few kilometres at Bayerisch Eisenstein. The name in German evolved from the name in Latin whose meaning is unknown.