Here we look at 12 of the most vulnerable properties whose once-mighty past gives way to a fragile future.
1. Brough of Birsay, Orkney
2. Bonawe Iron Furnace, Loch Etive, Argyll
3. Cambuskenneth Abbey, near Stirling
Finlay McWalter/Creative Commons
4. Castle Sween, Loch Sween, Knapdale, Argyll
Creative Commons/Mike 138