Bell of St. Peter - 24 tons
For a size comparison, the visible part of the clapper (what we see below the rim) is about six feet long. (see description) The 24-ton Bell of St. Peter was cast in 1922 and is the largest free-swinging bell in the world. It was commissioned the year before that by the Friends of the Cathedral for a strike note of perfect C and a first overtone E. Only one foundry (Ulrich) offered a bid.
For more on the bell and all other bells at the Cathedral, go to the Cathedral home site:
http://www.koelner-dom.de/domglocken.html?&L=1