Geek pretty much has it right. It's rather cynical to think that an area has to be packed with V12s to make it world-class, although it's true that hard routes/problems attract attention from the top dawgs, which gets attention in the mags, which draws the attention of Joe Gumby or Jaroslav Gumbjercjzowicz or Jose Gumbero to it, resulting in world-class status. You need a lot of rock (make that a lot of GOOD rock), a nice setting, variety variety variety, access, etc.