Just ran across the Mario Righini Car Collection on SCD. Wow. On top of being housed in a 15th century castle in Italy, Righini's collection includes the very first Ferrari, one of the extremely early Karl Benz cars, plus way too many incredible cars to list. I've never heard about this collection before...not sure if this qualifies as a "barn find" but perhaps it is the new and improved find...a "castle find".
Here is the story and pictures:
Mario Righini Collection -- Photo Gallery | Sports Car Digest