It weighed almost 20 tons and was 17 feet long. Cast in bronze by Munir Ali, and brought to the Ottoman Turk Army in Constantinople by Urban, a 15th century Hungarian gunfounder, the gun was used to attack Byzantines who laid siege to the city. The Dardanelles Gun was partly responsible for the fall of Constantinople. This gun was a wonder of its day and could lob a 2000-pound projectile almost a mile. It sat in its carriage for three centuries and was responsible for a fairly successful bombardment of British naval forces at the beginning of the 19th century. It was muzzle loaded and operated by as many as fifty people. It required hours between shots just to charge and load.
The gun now rests in Fort Nelson at Portsmouth.
Source: Wikipedia; F. Charles, “The ‘Dardanelles’ Gun at the Tower”, Antiquarian Journal