Dunnottar Castle, one of the most spectacularly situated castles in Scotland, on a rock promontory 2 miles south of Stonehaven. There has been a fortification here since probably the first century, though not as magnificent as the present ruins were.
The name is from the Pictish "Dun Fother" probably meaning "fort of the low country". The area of coast it lies in is known as "The Mearns", once the easiest way to reach Moray and beyond. From Dunnottar it was easy to patrol this area as a gateway.
The rock on which the castle is built is remarkable and almost unique. The entire peninsula consists of boulders and pebbles embedded in a red rock and looks, for all the world, like a fruit cake, perhaps that is why the conglomerate is called "Pudding Stone". It dates from the erosion of the Grampian Highlands in a very dry climate over 400,000,000 years ago. The conglomerate is so strong that cracks pass through the boulders and not around them.
(A day out I suggest is a walk at Lunan Bay in the morning, lunch at But 'n Ben's and then an afternoon visit to the House of Dun & Dunnottar Castle.)