Gibraltar is one of the best-equipped
intelligence gathering stations in southern Europe. Day tourists will just notice some smallish radar installations on top of the Rock, some roads that are for the use of the
military only and of course, the naval base.
Radar and sonar surveillance covers a large part of the Mediterrenian Sea, as well as a huge patch of the Atlantic ocean. Local military (the Gibraltar Regiment) might be the only armed force in the world specialiced to fight in tunnels - Gibraltar has by far more tunnels than roads, of which the majority hosts a military base.
Apart from living quarters, you will find huge storage rooms, a water purifying plant (which explains the waterfall on the Rock), ammunition depots and even a quay for submarines that was used for supplies in WW II.
Another noticeable detail is the 1800m runway of Gibraltar's airport, which is built mostly over water. The main road from Spain crosses the runway - which means that traffic stops, a plane lands or takes off and traffic resumes. Due to the short runway, only rather light aircraft can land on Gibraltar, the "national" carrier, GB Airways providing rather cramped flights from and to London and Morocco. As the paines are not allowed fly over Spanish soil, landing on Gibraltar is quite an experience. Duty-free prices in the tiny airport shop are very slightly lower than those on Gibraltar itself - the place is an oasis for drinkers and smokers. Hotels, however are expensive - due to the main industry, offshore banking.