Don't know why I watched any of The Speech (flipping through channels), but I have to disagree with folks who say it's a Greek Temple. Greek (and Roman) temples were rectangular. See this page for discussion, with many, many floor plans. Rectangular. This was curved. Not a Greek temple.
However, there is a name for it: a folly.
You'd think that people as smart as the Democrats would have someone that knows this. Maybe they do, just nobody has the stones to tell the Higher Ups.