You can hardly make a TL;DR here - the second paragraph is 100% interesting:

Orban managed to build this giant cannon within three months at Adrianople. Due to its size, it was dragged by 60 oxen and 400 men to Constantinople.[6] The cannonball, which could be shot at a distance of one mile, weighed 1,200 pounds.[4] It was horribly powerful, and when it hit, it caused massive damage to Constantinople’s walls. The cannon also killed some of its operators.[1] Additionally, due to the material the cannon was constructed of, and the intense heat created by the charge after each shot, the barrel had to be soaked in warm oil to prevent cold air from penetrating and enlarging the fissures.[3] The heat also prevented the cannon from being fired more than three times per day. Ultimately, it lasted all of six weeks before becoming non-functional.