In Scotland there is a little castle on Loch Ness called Urquehart Castle. Nobody knows who built it or why. Certainly not a bunch of guys that drank beer and went fishing there years ago. Maybe it had another purpose. The rain in the summer there is about the same temp as the water temp. I skinny-dipped around there once and that is a very deep glacial lake. Cute little red heads live around there that like to fish. Inverness has a nice restaurant that serves steamed or fried fish. Dunvegan is on the Isle of Skye and it's sort of like Kansas. Nice people there.
http://www.castles.org/Chatelaine/URQUHART.HTM
http://www.undiscoveredscotland.co.uk/drumnadrochit/urquhart/
From the looks of it, I was gonna say it was built in the Middle Ages. A lot of castle building involved using stones from previous structures, other crumbling castles or walls. It was faster to "borrow" than to start from scratch.
Text from the second link I posted...
"Opinions differ as to whether Urquhart Castle was originally the site of a Pictish fort dating back to a visit by St Columba in 597, but there was certainly a Pictish settlement in the area at the time. The first real evidence of anything recognisable as a castle dates back to the years following 1230, when Alexander II crushed a revolt in the province of Moray, to the north, and decided to defend this strategic route."
From what I can tell, my MacBean ancestors were from Iverness. Maybe they had a hand in building it. :o)