The title link is to a PDF book collection about important doorways,
and Chapter 1 is about what archeologist Nawafleh and his partner found
in the underground rooms, solving some dating problems and indicating
what the Petra Treasury (or Al-Khazneh) was used for and when it was built.
The PDF may not display inline on some browser versions, so in that case
right-click to save the link or download the file to read it. It's very