Amphitheaters are large, open-air venues designed for public spectacles, such as gladiatorial contests and theatrical performances. They are characterized by their circular or oval shape, allowing for excellent sightlines and acoustics, making them ideal for large audiences. Historically, the most famous amphitheater is the Colosseum in Rome, which could hold tens of thousands of spectators. These structures played a significant role in ancient cultures, serving as centers for entertainment and social gatherings, and many have influenced modern stadium designs.