This was part of the Week of Adventure Locations, and it was Location number 6. It is located along the Greywater River between the Darkearth Plains and the Sildur Reaches.
Adventure Location: As the Greywater flows under the King's Highway, it goes through an impressive tunnel, burrowed out and lined with very thick slate tiles throughout it's massive arch. The interior height of the arch is nearly 160 feet, higher in some spots (the top surface of the King's Highway, in this area, stands some 300 feet up over the plains around it). The river banks go right up against the tiled walls of the tunnel. About half way through, on the western wall, there is a large opening that goes back into the mound of the King's Highway.
|Side passage from the Greywater River|
|Underground City of Ohn Ohnan|