The Sixth Episode. The set was divided into four "zones" set in different periods of time and space. For the first three series, the zones were Aztec, Futuristic, Medieval and Industrial. From series four onwards Industrial was replaced by Ocean (set on the S.S. Atlantis, a sunken ship trapped in an air bubble on the edge of an abyss in the Pacific Ocean). At the centre of the maze was the Crystal Dome, a giant geometric acrylic glass 'crystal' where the teams play their final challenge after playing games in each of the four Zones.