Complex sentence: The two major carnival events in Germany are the Mainzer Fastnacht and the Kölner Karneval, although both cities are in the Rhineland region, the tradition is practiced all over Germany.
Split into simpler sentences: The two major carnival events in Germany are the Mainzer Fastnacht and the Kölner Karneval. These are both in the Rhineland region, but the tradition is practised all over Germany.