Professional circus artists were known as early as ancient Egypt. But the first substantial building constructed specifically for the circus did not open until August 4, 1777 in London. A retired cavalry corporal Philip Astley built a circular arena 42 feet in diameter, but for some reason named his establishment “Amphitheater.” Astley's Parisian followers, the Franconi family, also began to call similar establishments amphitheaters. But then Napoleon I forbade entertainment institutions (except for the privileged ones) to be called theaters. But the cunning Franconi found a way out of the situation: they changed the name for the “Olympic Circus.” The only thing that changed was the name, but not its shape or size. Since then, the first Astley Circus, the arena has remained 42-feet, or 13-meter, as we say. No superstition, just pure science: the centrifugal force created by a horse galloping in such an arena is ideal for the rider.