Thanksgiving Point, Salt Lake City
If you don't mind taking a drive, then I think Thanksgiving Point is really worth it. My husband and I like to look at all of the plants and garden design ideas. It is big and spacious, with little sitting areas indispersed all throughout the gardens. As we have only gone at night, we've never been inside the Atrium or the stores there, but it was always peaceful and quiet just taking a walk when we just wanted to have a nice date.
Great place to visit even with small kids. There wer lots of things to see and lots of hands on items for the kids to touch or play with. The displays were very informative. Took us about an hour and a half to wander through all the displays.