On the way to Oppenheim, the vine-covered hills parallel to the Rhine gradually steepen. Then, unexpectedly, the spires of Oppenheim's Gothic Katharinenkirche come into view. The contrast of its pink sandstone facade against a bright blue sky is striking. Built between 1220 and 1439, it's the most important Gothic church between Strasbourg and Köln. The interior affords a rare opportunity to admire original 14th-century stained-glass windows and two magnificent rose windows, the Lily Window and the Rose of Oppenheim. The church houses masterfully carved tombstones, and the chapel behind it has a Beinhaus (charnel house) that contains the bones of 20,000 citizens and soldiers from the 15th to 18th century.