Cyclocross is probably the most accessible variety of all the cycling disciplines, so it's lots of fun to come watch! Unlike road cycling where racers whiz by and are gone, or mountain biking which is held hours away on narrow dirt trails, cyclocross can be held at a local park. This makes it easy to get to, and once you're there, it's easy watch the race unfold in front of you. Courses twist and turn using all available hills, sand pits, paved roads, and strips of grass. Since courses are typically less than 2 miles long, it's easy to stay in one place and watch racers go by, or wander from one side of the course to the other in a matter of minutes.
On this course map you can see how tightly the course is wound around three different soccer fields, and doesn't even make it to the other side of the baseball fields!

 Sacramento Cyclocross course map at Lembi Park in Folsom