There were numerous arena incarnations used during the original run of "Robot Wars" on the BBC. These arenas were also used by international versions such as "Robot Wars: Extreme Warriors" in the United States. The arena was approximately . For Series 1 to 3 the arena was not enclosed as such, as the audience were raised above the arena. The increasing sophistication of weaponry from contestant robots – most notably demonstrated by Hypno-Disc in Series 3 – as well as arena hazards prompted producers to enclose the arena entirely in a perspex box high from Series 4 onwards, to protect the audience and production team from debris.