Complex sentence: The major prerequisite for the construction of the Sorpe dam was the completion of the "Röhrtal" railway on June 1st, 1900, a standard gauge "Kleinbahn" connecting Sundern to the "Obere Ruhrtalbahn" at Neheim-Hüsten.
Split into simpler sentences: The major prerequisite for the construction of the Sorpe dam was the completion of the "Röhrtal" railway on June 1st, 1900. The standard gauge "Kleinbahn" connects Sundern to the "Obere Ruhrtalbahn" at Neheim-Hüsten.