Why do things wind up under the ground? I suppose that many things exposed to the great outdoors sink into the earth a bit every time it rains.
Let's assume you mean very ancient structures.
One of the ways is that old structures are used as foundation for newer ones.
The other way is that they are covered in silt.
There are many examples of this around the world and they point back to a world-wide flood around 13,000 years ago.
Secret societies often built structures underground so they could conduct their ceremonies in secret.
Space dust - the Earth grows by 1" per year due to the accumulation of space dust. Look what happened to Mars - even the oceans were eventually covered up by space dust. Forget global warming; it's space dust that will eventually be our downfall.
The information above has been determined to be fake but accurate. Be sure to tell everyone you meet about the dangers of space dust and how it is burying us at an alarming rate. You can demonstrate the truth of this looming disaster by the fact that all the old stuff ends up under the dirt (space dust).
What’s even weirder is that the monoliths on Easter Island are not just carved faces- they are whole statues from head to toe- buried in the ground up to the neck.
That just kills every theory how they carved these heads and ‘walked’ them to their places, now they would have to figure out how they ‘walked’ a statue 3 times taller, then dug a whole and buried it.
I’m not saying it was aliens... but it was aliens.