My favorite is definitely art museums.
I used to live about an hour from New York City, so I was pretty spoiled by great museums. When I moved to Missouri I didn't go to the St. Louis Art Museum for 8 years because I was sure it would be very disappointing. I could not have been more wrong! I walked through that place with my mouth hanging open the entire time. They actually have one of Monet's Water Lilies ! And one of Degas' Ballet Dancer Sculptures! And an El Greco! and the list goes on and on.
So if anyone is in the St. Louis area and has not been there, by all means go to the Art Museum.