The Stone Barrow is only a stone's throw away from the White House. This massive barrow marked the entrance to a region of the Great Underground Empire that had once been linked with to the portion beneath the White House. In the east face was a huge stone door which was open until the unknown adventurer, which would become the Second Dungeon Master, entered--the door closed behind him and possibly has remained closed ever since. In the mid-tenth century, the tomb was hidden from the normal adventurer, but shortly after, the renovations under the management of Morgrom the Essence of Evil saw the defoliation of the forest which hid it and a boulder-lined path which led past the white house and right up to the stone door.

After the collapse of the First Age of Magic, a bickering and a flickering torch were placed in sconces on either side of the entrance--both which were removed by Brog when exploring the regions beneath the White House.

SOURCE(S): Zork I, The Zork Chronicles, Zork:Grand Inquisitor