In 1860 a civil engineering contractor was awarded the contract to build Nothe Fort. The first stage was the construction of a sea wall that would allow a level site to be formed on the sloping ground at the end of the Nothe Peninsula. However, due to financial problems, they failed to complete the wall. This responsibility and the construction of the fort were then given to 26 Company Royal Engineers.
The fort is constructed on three levels. The lowest level, Magazine Level, was originally designed to store gunpowder and shells. The middle level, Gun Deck Level, was designed to accommodate 12 heavy muzzle loaded cannons and provide accommodation for the soldiers manning the cannons. The top level formed the ramparts and provided a raised platform that could be used to fire muskets and light muzzle loaded cannons during an attack on the fort.