The cliffs in this area are made of limestone that is around 20 million years old. The limestone has lots of fossilised marine invertebrates (I think that means shells, as you can see them all sticking out of the rocks) in it, and it is easily carved away by sea water.
It has made the incredible cliffs, caves and holes that we have been admiring recently.
These rocks are at Algar Seco, and we spent quite a while clambering all over them.
Our latest hotel is about a mile away from them in a lovely little town called Carvoeiro, although we have no idea how to pronounce it.
The tide is out in this photo, but Darren has splashed out on our hotel and we have a fantastic sea view.