Complex sentence: During the Middle Ages only two bridges across the Selz existed: the "Lower Bridge" at the ancient Altengässer Tor and the "Upper Bridge" at the Ohrenbrücker Tor.
Split into simpler sentences: During the Middle Ages only two bridges across the Selz existed. The "Lower Bridge" at the ancient Altengässer Tor and the "Upper Bridge" at the Ohrenbrücker Tor.