The Commissioner's refers to the administrative quarters of the individual who represented the British Government in various parts of the British Empire. Today, the chief representatives of the UK in Commonwealth countries are known as High Commissioners.
Gibraltar (sometimes referred to as the Rock of Gibraltar) is situated at the southern tip of the Iberian Peninsula, at the entrance to the Mediterranean. It came under British rule in 1713, and remains one of fourteen British Overseas Territories. Historically, it has been an important Royal Navy Base.