Cyclo cross is a great workout that challengers many of the components that good cyclists from most cycling disiplines must develop.
Aerobic Conditioning -Skills - Balance - Strength from the heavy going - Pace judgement - these are just some of the areas that benefit. not to mention the variety and change from road or track cycling.
I include some photos from A race in Corkagh Park which is a Dublin City Council amenity just off the Naas road about six miles from Dublin City Centre. The park also has a well stocked lake where the public can fish.
The field in this event is comprised of mountain bikers road and track riders
Note the bikes with knobbly tyres for good grip on the cross country terrain. Brakes with lots of clearance from the frame so that mud does not block the wheels from turning.