We visited the National Art Center in Nogizaka near Roppongi. We took a bus to Roppongi and then walked down to the museum. You can also take the Chiyoda subway line, and get off at Nogizaka and the station is linked to the museum.
They have a nice restaurant upstairs where people were already lining up before the opening time.
Surrounded by art pieces inside of modern architecture, it was nice to walk around and relax. There is a museum store on the basement floor.