Pretty much equal distance - Waterfront and L'enfant are your options
Waterfront or L'enfant. L'enfant is actually a little closer to the Anthem, I think, but if you want to check out the area go to Waterfront
The venue suggests L'Enfant. They have flags that lead you from L'Enfant to the Anthem. That said, you can't get lost from Waterfront but it is only Green Line where as L'Enfant gives you other options.
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