It is an octagonal-shaped chamber about 30ft wide (which would be crowded if the whole company of nine were to push in). The ceiling is as the inside of an octangonal pyramid. Standing in the center of the chamber is a 3ft wide, four-sided stone menhir with steeply pitched sides, tapering toward a near-point some 8ft from the ground. Each of its sides faces one of the four exits from the crossroads room, and is graven with alien runes.
To the left, a narrow stair descends into darkness. To the right, and directly ahead, dark passages continue at this level.