    Madain Saleh is the southernmost outpost of the Nabateans; these
    tombs are from the first century, CE. KAUST arranged this CAVEcam
    expedition as part of a training session conducted by Dick
   Ainsworth, Tom DeFanti, and Dan Sandin, for KAUST Visualization
    Lab team members.  This image shows a large chamber hall (Al-
    Diwan) carved from the sandstone, featuring seats along the walls.
    See http://saudi-archaeology.com/gigapan/al-diwan-madain-saleh/
    and http://en.wikipedia.org/wiki/Mada'in_Saleh