I tend to think of caves as being roughly horizontal holes in the ground with low ceilings, that occasionally open out into large caverns or plunge down cracks to lower levels.
It is the sheer verticality of St Michaelʼs Caves that comes as a surprise.
I suppose that it shouldnʼt do, given that Gibraltar is a chip of limestone that was broken off and tipped on its side when Africa bumped into Europe.
If the western side of the Rock were horizontal, then so would the cave system.
The rock formations are quite breath-taking, and if you can catch a lull between the successive waves of tourists 'doing' the Upper Rock Tour, the place has a cathedral like serenity.
In fact, the largest of the caverns is called the Cathedral Cavern. It was opened out and given a concrete floor during the Second World War, with view to turning it into an underground hospital. This never came about, and the area is now a unique, if damp, auditorium seating up to 400 people.
If you are on foot, St Michaelʼs Cave is best reached by taking the cable car up to Signal Hill and walking down St Michaelʼs Road to the caves.
Joint entry tickets to the caves and a number of other attractions are available with your Cable Car tickets. There is a small café and souvenir shop on site. Watch out for the monkeys though.