As recently as a century ago, scientists doubted whether the universe extended beyond our own Milky Way — until astronomer Edwin Hubble, working with the world’s most powerful telescope in the mountains high above Los Angeles, discovered just how vast the universe truly is. Visit the underground vault of the Carnegie Observatories, where paradigm-shifting discoveries are annotated by hand on glass photographic slides; and the historic Mount Wilson observatory. Learn more at Carnegie Observatories.