Atlanta news station CBS 46 aired footage of a large set for The Hunger Games: Mockingjay taken from their chopper. The set, which is located in Norcross, Georgia, is inside a massive area closed off by stacks of shipping containers for privacy. The large lot was formerly a factory for OFC.
MOCKINGJAY SPOILERS FOLLOW
In screencaps from the video, you can see several large sets with giant green screens.
In the shot below, you can see several large black objects. Could it be that these are the pods that Squad 451 encounters in the Capitol?
In this last image you can see another large set:
Sound off in the comments with your speculation on what these sets are for!