@Flick7 is correct the reference is to a deleted level named Element 111 Rg that was a projected top 1 back in the early days of Geometry Dash. It was completely wiped from existence and there are no copies of it or hardly any videos of it. It was removed due to having a clever secret way where if you held at a specific frame you could hold the jump button over every spike jump and you could essentially skip the entire level.
