Construction began as far back as 1150 but the cathedral underwent a number of setbacks and transformations before its completion. One of the most significant transitions took place in the 15th Century at the time of the austere Reformation. St. Pierre Cathedral was stripped of its altars, statues, paintings and furniture with only the stained glass windows remaining. The initial Gothic facade of the Cathedral was also later modified to its present mid-18th-century Neo-Classical style. For many visitors, one of the highlights is the breathtaking panoramic view of the city at the top of the steps of the narrow winding staircase in the North tower. The cathedral also has a very important archaeological site dating from the beginning of Christianity.