St. Pierre Cathedral is the heart of Geneva's Old Town and its most important religious landmark. Built in the 12th century in Romanesque-Gothic style, it became the center of the Protestant Reformation under John Calvin in 1535. Visitors can climb 157 steps to the North Tower for breathtaking panoramic views of the city, Lake Geneva, and the Alps. Beneath the cathedral lies an archaeological site revealing Roman-era remains and the evolution of the site over 2,000 years.