Caramoor in Westchester County, NY, is a year-round treat but most fun for their outdoor summer concerts. Like Tanglewood, really, but without the Great Lawn. For classical music, they get the worldwide best and it's an elegant venue. Their Beethoven Violin Concerto yesterday was dynamite. Always loved that piece, but who doesn't?
For a cool long-weekend spot for outdoor activities (and it is cooler in those mountains, but not far north of NYC) - Mohonk Mountain House. This venerable place was a favorite getaway of my Grandpa. Some of my kidlings were there this weekend, sent me this pic from a stroll (or horse) around their multi-thousand-acre property: