Complex sentence: The Stadtbahn Karlsruhe is a German tram-train system combining tram lines in the city with railway lines in the surrounding countryside, serving the entire region of the middle upper Rhine valley and creating connections to neighbouring regions.
Split into simpler sentences: The Stadtbahn Karlsruhe is a German tram-train-stadtbahn system in Karlsruhe and its region. The transport system combines tram lines in the city with railway lines in the surrounding countryside and thereby opens the entire region of the middle upper Rhine valley and creates connections to neighbouring regions.