Here is one of the best Concrete Skateparks I have found around the web and its called Bologna Skatepark in Italy.

Building concrete skateparks is a huge job so you should tackle it in a few different sections. This will help control the amount of concrete going into your skatepark at one time. Here is one formula for pouring concrete into a skatepark. For skatepark construction use 4000 psi concrete to a minimum depth of 4 inches. This is poured over a minimum depth of 4 inches of gravel. What you don’t want to do is get the lowest bid from your local city and have your sidewalk guy pour you concrete skatepark for you.

Here is a list of some of the countries best Concrete Skatepark Builders

Dreamland Skateparks
Airspeed Skateparks
Grindline Skateparks

Here is a video clip of Bologna Skatepark being ripped to shreds by some of the best skateboarders in the world.