Where do we reckon are possible storage locations for retrieved craft/NH technology?

I’m aware of the alleged big players such as Battelle, Lockheed Martin, Raytheon etc. I’m also aware of some of their “conventional” sites but in regard to the above, are their any decent rumours, discussions or any other theorising around where they may be keeping such technology?

I do wonder are they in the middle of nowhere or hidden in plain site. If fully intact, where are they being kept?