Reconciling objects from DARMC with Pleiades today, I came across the late antique monastery at Horeb Mons. I don't have a copy of the Tabula Imperii Romani with me this morning and won't be able to check for a while (WorldCat says there is one at the Colorado State library), but this looks to be Saint Catherine's Monastery (a UNESCO World Heritage Site). The Pleiades entry for this place is surprisingly skeletal.
The first occurrence of "Horeb", חֹרֵב in Hebrew, χωρηβ in Greek, is in the Old Testament's Book of Exodus. The Barrington Atlas, on which Pleiades is largely based, does not attest to a location for the biblical Mount Horeb itself.
I've never been to the Sinai Peninsula, but visited Mount Horeb, Wisconsin a few times in the 1990's. Its Mustard Museum may never be recognized by UNESCO, but is an important stop for a completely different kind of pilgrimage.
Update (2011-08-18): I've checked out the TIR and brought it back to ISAW West; Saint Catherine's is at Tou Batou, not Horeb Mons.