The cathedral is an architectural masterpiece dating back to the 13th century. Spanning the threshold of the Romanesque and Gothic periods, it took some 80 years to complete the colossal building. In fact very few cathedrals in Germany are as richly adorned as this one. A marvel of the late medieval times, the astronomical clock features a calendar extending to the year 2071, with glockenspiel workdays at noon and Sundays and holidays at 12:30 p.m.