Mobot is a pleasure to spend a day or three . They are one of the premier gardens in the US. There knowledge data is unsurpassed. They still sponsor expeditions to far flung lands to further the science of botany. The viewing gardens are massive, set out under themes, and then there's the Geodesic Dome a Buckmaster Fuller creation that houses all topic plants. Take a day just to get through that repository.
They also operate a couple of 'subsidies', the Butterfly House in Chesterton, Mo. and the Shaw arboretum.
It is a truly an amazing place. We try to go there at least once a year. You can't help but walk away profoundly altured by the enlightenment received.
The thread "Missouri Botanical Gardens - St Louis (MOBOT)" in
Public Gardens Photo Tours forum. - trip thereto when warm weather
The thread "MOBOT Feb.2013 St Louis" in
Public Gardens Photo Tours forum - trip thereto in the winter, highlights the indoor tropics noted above. It's called the Climatron.
They have an excellent site should you need more info in making such an expedition.