....Duuhhhh
The Jones Assembly is located right behind 21C. It's a "must go to" spot, even if you don't want to eat or drink. Enjoy the space. You may even be able to catch a concert.
Perfect outdoor spot when the weather is nice. It's never packed and an extraordinary view of the city.
The largest permanent exhibit of Chihuly glass. A must see if you're into that kind of stuff.