By far the most comprehensive study of the subterranean structure known as the Osireion, its relationship to the main temple complex of Seti I, and surrounding sacred landscape at Abydos. The Osireion contains an enormous wealth of information with its encyclopedic array of New Kingdom Underworld Books and provides a unique insight into the ancient Egyptian worldview, circa 1300 B.C. at the beginning of the Nineteenth Dynasty, following the tumultuous Amarna Heresy. It was built by Seti I as part of his program to re-establish the abode of Osiris, abolished by the heretic Akhenaten, thus explaining its form as a subterranean architectural rendition of the Duat itself, the realm of Osiris as Ruler of the West. Built on the same axis as Seti's Mansion of Millions of Years, it was from the beginning to have been an integral part of this complex. Its ancient name, "Beneficial is Menmaatre (Seti I) for Osiris", points to is purpose. Two graffiti from Dynasties XXI and XXII provide further insights as to how the ancient Egyptian priests perceived this unique structure, calling it "hidden/mysterious place of the Duat of Menmaatre" and in a greeting "Hail to you! Isis in the birth house".