Since a lot of us equate the circus with lion tamers and acrobats (and don't you worry, we'll get to those), it might surprise you to learn that the horse originally made the circus a hit. Phillip Astley was a former cavalry rider who opened a riding school in London in 1768 [source: Jando]. The big innovation at the place was the "circus," or ring, which allowed spectators to watch the riders perform tricks from every possible vantage point. It's not easy, after all, to have enough space for a straightaway where audience members can see. Astley's 42-foot (12.8-meter) diameter ring is still used as the standard measure for circuses [source: Jando].
Astley began putting on shows of equestrian stunts, drawing people to the ring with his animals' feats. By 1782 he had started a similar equestrian circus in Paris, and competitors began popping up [source: Jando]. However, the circus wasn't just a horse and pony show by now. To add a little excitement to the proceedings, Astley started adding in small little sketches between horse exhibitions.