h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Casa Loma - Toronto, Canada. Built at the end of the nineteenth, beginning of the twentieth century by some Canadian industrialist who desperately wanted to be royalty. Has wooden walls carved by Germans, an underground swimming pool (unfinished), secret passages, a tunnel to the stables and a beautiful view of the city below. Also some weird dragon/bell sculpture and a made up legend to go with it. A wonderful folly and he went bankrupt doing it.
Dumbarton Castle - Dumbarton, Scotland. Its Macbeth's castle, when he was king. It guards the entrance ot the Clyde, is built on a huge rock, and has been re fortified up until the Napoleonic Wars. Lots of up and down walking but some stunning views from the battlements.
Berwick - Northumbria, England. Well its actually a town which changed hands between the English and the Scots something like 13 times (I need to check that). It has the best example of Elizabethan defenses atill standing, and I wouldn't attack them.
Culzean Castle - Ayrshire, Scotland. Another brilliant folly it is perched on the sea cliffs with beautiful views. Totally rebuilt in the seventeen hundreds by Robert Adam it appears on the back of the Scottish Five Pound Note. Oh and it has some lovely grounds which you can take days to explore.