Big Dumb Object-What everybody found out Equestria was when they dug deep enough to hit the computronium layer five kilometers down in 1018 ANM. When they hit this, Equestria and the Moon briefly became Big Dumb Moving Objects as the entire solar system changed over from an Aristoleian system where the Two Sisters raised and lowered the Sun and Moon, to a Keplerian system where everything orbited the Sun.
Needless to say, this shocked a great number of people, allowed Princess Celestia and Princess Luna to sleep in for the first time in nearly three thousand years, and was one of the greatest inspirations for space exploration. This meant that Equestria itself would be known as the first ever discovered Precursor artifact.
Other Big Dumb Objects have been found, all of them of Precursor manufacture. From the Silent Cube to the Rings, the one thing that seems to be common about Precursor artifacts-they don’t think small.