If you think, Gibraltar is in the southern part of Spain, you're absolutely right. Still it belongs politically to Great Britain. That is the reason, why Gibraltar is described on the Great Britain pages.
Gibraltar is full of natural caves and tunnels, some 150 principal and natural caves have been counted until now. The sea was some 100 meters below the actual level during ice age. So many caves formed during the ice age are situated below the present day sea-level.
One of the caves of Gibraltar is a regular show cave.