Dominating the city skyline, you can’t fail to notice it: the Kaiserburg. At the time of the Holy Roman Empire, the castle was occasionally home to each of the emperors, and in the Middle Ages, it was one of the most important royal palaces. The sights here include the new castle museum, the palace with the emperor’s living quarters, the Romanesque Double Chapel, the Deep Well and the Sinwell Tower. The neighbouring garden is a must-see too. It might be small, but it’s a welcome contrast to the hustle and bustle of the city and is popular with residents too. The castle's garden is open from April to October.