Introduction to the clock tower: The clock tower, known as "Liesl" by the locals, is a landmark building in Graz and can be seen anywhere in the city. The clock tower was first built in the 13th century and was converted from a watchtower. The big bell rings three times a day (7:00, 12:00 and 19:00), ringing 101 times each time, reminding people that it was made of 101 cannonballs. Inside the tower is the Castle Hill Museum, where you can see the defense model of Castle Hill 200 years ago and the prison at that time.