Photo from Pez Cycling News. Follow the link for a good article and more definitive photos.
When it's dry, it is dusty, when it rains, well, when it rains, all hell breaks loose. There are two preferred lines, either you ride the crown of the road or you ride in the gutters and you had better be close to the front. Bikes are equipped with fat tires, double-wrapped bars, longer forks and chainstays, aluminum bars and heavy-duty everything. There have been 'cross bikes and suspensions employed to help survive the cobbles but at the end of the day, only the strongest riders who are packing a load of good luck have a chance to carry home the cobblestone that serves as the trophy.
There is a reason that so many bikes, accessories, and components carry the name "Roubaix".