I went to visit dartmouth College this weekend and while there took a trip to visit The Fells historic site and gardens once owned by John Milton Hay.
The Fells is located in New Hampshire, and is well worth a visit. The Old Garden (1909) was very nice, but the most spectacular site was the Clarence Hay Rock Garden (1930s) which had over 300 species of alpine plants in a variety of microclimates.
Website: https://thefells.org/