St. Peterskirche is one of the three main churches in Zurich, Switzerland. The other two are the Church of Zurich and the Cathedral of Notre Dame of Zurich. St. Peter's Cathedral is also the oldest church in Switzerland. Its name can be found in the historical documents of 857 A.D. Before the Reformation in Switzerland, St. Peter's Church was the only parish church in the city, and the rest were attached to monasteries. The church clock tower, which was built in 1534, has the largest church clock dial in Europe. The dial diameter of the clock is 8.7 meters, the hour hand is 3 meters long and the minute hand is 4 meters long. The church bell tower is used to monitor fires. It is said that once a fire alarm occurs, a flag is stretched in the direction of the fire to tell people where to put out the fire.