Site 1 also known as Erebus is the largest of the three archaeological dig sites on Mars. It was discovered in 2115. It is made up of a series of chambers and underground tunnels covered in glyphs. Site 1 houses an ancient Martian portal, as well as the artifact. By the events of Doom 3, the UAC science teams on Mars were still working at Site 1.
According to James Holiday's PDA, the UAC suddenly ended all research in Site 1 on November 15, 2145 - the day the events of Doom 3 take place.