The aliens have left now(wrapped up less than a year ago) but they were connected to the ones that introduced Adrenochrome to man and the Kazahrians/molochites several millennia ago and they basically have a deity like worship going with them.

So all the high profile visits are basically people going to see their alien overlords(I shit you not)

There is some stuff and evidence of structures that can still be seen on goolag earth but if you are in Antarctica there are so many of them and they're generally so easy to find that having zero control over who goes there is not something they are willing to do.

People have tried and wound up dead and the judges have repeatedly warned people to stay away from Antarctica as currently trying to go there without permission is likely to be a protracted version of suicide(go there and you will die and you will probably die badly).

Don't know who is currently in control of the place though, could still be the alien overlord worshiping types, not entirely sure the whitehat's would kill you to keep that secret but I wouldn't rule it out either...