Monoliths similar to the one in Nevada appeared in different locations around the world about four years ago, including one in the Utah desert.
That one left local authorities baffled after it was discovered by a helicopter pilot flying overhead in November 2020.
Another one was found in Romania around the same time, as was one in California and on the Isle of Wight in the English Channel.
Speculation brewed then as to who may be behind them, with some wondering if they were part of an art installation. But no one has come forward since to claim they were behind the structures.
Another monolith more recently appeared on a hilltop in Wales in March. Observers said the sculpture looked perfectly level, but it offered no clues as to who could have placed it there.
While the mystery behind the monoliths remains, Las Vegas authorities used their latest discovery to remind people hiking in the Nevada desert to be prepared for the hot weather and to stay safe.