LoL, that would give geologists a puzzler.
Huge Chalk hill in middle of Arabia.
Can we put a Cathedral on top of it? Go Full Gothic on them. :)
Well, let's ponder this.
If Mecca is buried in a chalk pile that would also cover their cubething. And if we extend that chalkpile to Medina we can cover the non-empty tomb of their profit, er, prophet. Doing so would remove any reason for the mooslimes to travel there thus no resistance to building a cathedral. Or anything else for that matter. ;-)
The fact that their profit, er, prophet is still in his tomb says enough..