Capri is actually quite a barren island largely made up of limestone. Weathering of the limestone has led to the development of some amazing caverns and rock arches.
The tour boats are met by oarsmen in much smaller rowing boats, and for a fee these oarsmen will row you across and into the Blue Grotto. A cable permanently attached to the cavern entrance is used to pull the boats inside. Guests are asked to lie down on the bottom of the boats to avoid hitting their heads on the entrance (it really is quite low).
Inside is a 'tingling on the back of the neck' experience. The water is an unbelievably bright blue and you just sit there gently rocking in your small boats in awe. We were lucky enough to have one of the boatmen burst into song - the acoustics would have made any of the great opera singers envious. The cavern is lit from beneath by light from other caverns further below the surface.
After visiting the Blue Grotto we were taken back to the tour boat and then travelled on to a small harbour where we left the boat and walked up to the township of Anacapri. You can take a bus up to the village but the walk was very pleasant. The view from Anacapri is also spectacular, in fact the whole experience is really one not to be missed if you happen to travel to northern Italy. Two thumbs up!