The Guardian of Earth is a very advanced machine of TL 12 . It was constructed/ created by an artificial Entity called NUCLEI .
It is not certain if the cave was a natural subterranean cavity or had been created by the TRANSPORT or the Guardian.
The cave also contained the "Guardians' Base ", the Cabinet of Greats and the RECORD .
The cave has a concealed entrance connecting it to a 12-mile long tunnel, which ends underwater in a deep lake.
Richard Stahl detonated a nuclear device in the Cave, destroying the Guardian and the Cabinet of Greats