The Eric Carle Museum is beautiful. I once went there for a talk given by local authors and illustrators, and Holly Black and others were there; I was impressed. It's had some good exhibits, too. (Though I've only been twice....)

I like the large, seasonal paintings in the main hallway. I tried to see about having a birthday party there for one of my kids when they were little, but it was SUPER EXPENSIVE, so I didn't.

The car garden is neat--is that in Northampton?