“landing pad for aliens”
That’s got my vote.
Why else do you think the government paid so much money for the site and then only to cover it up (literally) with dirt. ;)
Bordered by both a river and an ocean? The holes could have been used for season indicators or counters visible to fishermen, etc.
But if you want a UFO landing pad: The World’s First UFO Landing Pad is in St. Paul Alberta
“landing pad for aliens”
On balloons - from Mexico.