Fort Rinella is a Victorian Battery which was built by the British between 1878 and 1886 and it is one of four coasted batteries that housed an Armstrong 100-ton gun. In fact, it contains one of two surviving Armstrong 100-ton guns. The fort was built in the shape of an irregular pentagon confined by a deep ditch. It has two levels, an underground structure where one can find the loading-chambers and a ground level with accommodation for the soldiers and machinery chambers. In 1996, Fort Rinella was opened to the public as an open-air museum. The gun fired for the first time in 100 years on 21st November 2005 by the Chief Minister of Gibraltar. The gun is now fired once a year.