Here's a list of some of the biggest skate parks around the world. Every skater should plan on visiting at least one of these in their lifetime.
Black Pearl Skatepark, Grand Cayman Islands. This is the worlds largest outdoor concrete skatepark. It's size isn't justified by pictures that can be found online. The locals are awesome, too (having been to Black Pearl personally, I can vouch for them). This park has a lot of cool features, like an over vert half pipe, a half sphere, and a huge, deadly quarterpipe. There is a skull painted the giant quarter pipe, so you know it's dangerous. There are a few smaller ramps, too, for amateur skaters.
Camp Woodward, PA and CA. Woodward is more of an experience than it is a skatepark. It's not just limited to skateboards, either. Camp Woodward offers playgrounds for all sorts of extreme sports - from blading to biking, and, of course, skateboarding.
Kona Skatepark, Jacksonville, Florida. This is one of the oldest surviving skateparks. It's age is apparent, too. It shows skaters a time when downhill slaloms were the main event for a skate competition - there's a huge slalom in this park. It's still fun, just not current.
Lake Cunningham Regional Skatepark, California. This park is famous for its 70 foot long full pipe. Can anyone actually skate it? Probably not without being towed by an ATV or similar. There are plenty of pools and even a street course at this park. Bikes are allowed, but not in the bowls. Sweet.
Anyway, those are some famous parks. If you do visit any of them, please make sure that you take care of yourself by wearing proper safety gear. You can't skate with a broken head!