Schloßberg castle depicted in 1679.

The fortification of the Schlossberg goes back to at least the 10th century. In the mid-16th century, a 400 m (1,300 ft) long fortress was constructed by architects from the north of Italy. There are records of a cable-hauled lift being in use between 1528 and 1595 to move construction materials for the fortifications. The castle was never conquered, but it was largely demolished by Napoleonic forces under the Treaty of Schönbrunn of 1809. The clock tower (the Uhrturm) and bell tower (the Glockenturm) were spared after the people of Graz paid a ransom for their preservation.[1][2][3][4]

The remains of the castle were turned into a public park by Ludwig von Welden in 1839. The park contains the Uhrturm, the Glockenturm, a cistern (the Türkenbrunnen) and two bastions from the old castle. The Uhrturm is a recognisable icon for the city, and is unusual in that the clock's hands have opposite roles to the common notion, with the larger one marking hours while the smaller is for minutes. The Glockenturm contains Liesl, the heaviest bell in Graz.[1][2][5]

Near the Uhrturm a café with views over the old town can be found. Additionally, on the western side of the Schlossberg, there are two small cafés, one with table service and another with self-service. Next to the terminus of the funicular railway there is a hilltop restaurant with views of western Graz. In what was once the cellar of one of the ruined bastions is the Kasemattenbühne, an open-air stage for concerts and performances.[6][7]

Below the Schlossberg hill is an extensive system of tunnels, which were created during the second world war to protect the civilian population of Graz from aerial bombing. Some of these tunnels are still accessible, including a passage from Schlossbergplatz to Karmeliterplatz, but many are closed to the public.