ATLAS, the incredibly complex particle detector that processes the experiments running inside the even more incredibly complex Large Hadron Collider, is not open to visitors. But CERN has a compromise: an enormous, gorgeous mural of ATLAS' guts.
CERN commissioned American painter Josef Kristofoletti to create the rainbow cross section, which even at three stories high, is only a third of the machine's actual size. The things CERN does should never, ever stop being massively impressive to us—this should help. [ATLAS]