Tumbledown means falling, or fallen, into dilapidation. To me it sounds nicer than neglected, devastated, destroyed or ruined.
Oh and coincidentally*, my lovely romantic novel
Escape to the Country has tumbled down in price to just 99p/99c until 21st December.
The castle is Tarbert in Scotland. There are a lot of Scots towns and villages with the name Tarbert or Tarbet. That word means a narrow strip of land. It's quite often where two lochs meet.
There you go - two words for the price of one! You can't say I'm not good to you. Well, you could I suppose but I can't hear you from here.
*You didn't really think I planned this stuff, did you?