Superguns
A supergun is an extraordinarily large artillery piece. This size may be due to a large bore, barrel length or a combination of the two. While early examples tended to have a fairly short range more recent examples sometimes had an extremely high muzzle velocity resulting in a very long range.
Depending on the design they may be used to destroy heavy fortifications or are used to bombard an enemy from extremely long range.
Read more about Superguns: Late Middle Ages, World Wars, Modern Developments