In June 2017, the husband and I took our vacation up to Fallingwater at Mill Run, Pennsylvania. There was both the indoor and the hiking tour outside, this post will only cover the outside. The Bear Run Nature Reserve map is here. It’s about a mile trip surrounding the house and you have a guide, so no real self exploration allowed. I imagine that the Bear Run Reserve would be much more if you want to exert yourself.
However, the grounds were beautiful and here is an approximate route we took:

The water surrounding the area just felt so magical, as if we had found our way into a Lord of the Rings set and the Elves were about to show us Rivendell.