What's most interesting is by just crossing a border town of La Linea de la Concepcion, you'll find yourself immersed in 1960s England, using pounds instead of euros, speaking english instead of my miserable two-word vocabulary of spanish (gracias and si), london buses as well as red post boxes. It comprises of a small area 5 km long and 1.6 km wide, and one hell of a huge lime stone 426m tall (a major feature).
It has a little airport. You can actually walk or drive across the runway except the times of taking off and landing of planes. The most prominent feature is the rock itself which is the home to many apes. Other attractions are Michael's cave (big natural grotto), and the Great Siege Tunnels (place for gun emplacements).