I love "lost place" caches. However, here they only left the foundations of the buildings. Nevertheless, a very interesting place!
RexTrex and I were doing all the questions and computations and got it almost right. This is usually not enough, but with a group of other geocachers including the owners behind you, it is impossible to go to the wrong coordinates.
Thanks to winglen for designing the cache and helping us with one digit - Fogg