As others have said, the key is Antarctica. Why do world leaders secretly visit there? What's to see? Why are there multi military bases there? What is being explored? What is being kept secret?
A few things i've run across that *might* be true (I have no way to prove):
In addition, I've seen some information about the nαzιs having a secret base in Antarctica.
What's very interesting about Antarctica is the massive difference between its climate and that of the alleged opposite side of the globe. If in fact the earth were at that 23.4 degree tilt (interestingly, that's 66.6 degrees from 90), and that was responsible for the seasons, rather than the movement of the sun between the tropics lines (Cancer and Capricorn), their climates should be somewhat comparable, but they're not even close. Antarctica is FAR colder and more desolate and more barren. That would basically make a lot of sense on the most popular flat earth model, which has the sun moving much more quickly around the outer edge when it gets closest to Antarctica, so there would be much less sunlight there than there ever would be at the North Pole. Both should have a similar 24-hour sun, but the one video out there which claims to show it in Antarctica was clearly faked, with people demonstrating that the cloud patterns were identical at the beginning of the video and at the end. I'll find the details about the differences between the two "poles", which should in fact be very similar if the seasons were due to the earth's axial tilt.