Originally Posted by slims_s

Let's see... I'm taking Alpe d'Huez as the example, it is 13.8km at 7.9% average. Best time last year was 41' 21" (0.68916 hours) by Samu Sanchez, so the average speed was ~20km/h... holy s**t.
Pantani's ride on 1997, 37' 35", ~22km/h, hmmm... juicy

Source: http://en.wikipedia.org/wiki/Alpe_d%27Huez