Cyclo-cross is a discipline that combines characteristics of both mountain biking and road cycling. Standard cyclo-cross terrains include grass, forest trails, concrete, mud, and even sand! And that's not to mention the obstacles that will force you to dismount and run over them.
Cyclo-cross is a sport that has rapidly gained popularity, with tens of thousands of cyclists competing in fast-paced, frantic races on 2 to 3 km long circuits, primarily based in Northern Europe during autumn/winter. The good news is that this sport can be practiced all year round; you'll simply need the right bike.