It is a huge stonemound, with foundation stones, then larger wall stones, some weighing tons, and a stone and earthen roof. Inside a small narrow passageway to a small central chamber. An alter where remains of the dead are kept, dug up after being buried. At Newgrange, there is a small opening that lines up to let a single shaft of light flood the chamber for only a few minutes exactly at the sun rise of the winter solstice.
To stand in that chamber is an unforgettable experience. There is a lottery to get tickets each year for the limited space.
All built over generations, before the pyramids were built.
What the drone caught was the soil change, still visible after centuries due to the foundation stones.
You can’t begin to imagine the labor involved in transporting the rocks and their size from many miles away.