Capital South or Federal Center SW on orange/blue/silver lines are the closest to the Botanical Gardens. L'Enfant Plaza and Archives on yelliw/green lines are close, too. Assuming you will be coming in on yelloe/green line or switching at Metro Station or Gallery Place if coming in on the red line. The Botanical Gardens building is across from the south side of the US capital. There's a great photo op of the Capital from the botanical garden. Enjoy your visit!
We took the orange line but we came from New Carrollton station. There is a main metro station at Smithsonian station.
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