It's forbidden to go within 15km of Mecca if you're not Muslim.

You need a certificate signed by an Imam, which you can likely get at your local Islamic center. Challenges include convincing the Imam that you're not just getting it to sneak into Mecca, and being able to answer follow-up questions at the roadblock in Mecca, such as, "So you're Muslim, eh? Tell us the Five Pillars."

Mecca, Saudi Arabia is slightly different, of course.