Their contest is interrupted by the arrival of a fleet of massive airships, and the bizarre robots they unleash on the area.
Not long after arriving on South Island, Sonic the Hedgehog attracts the attention of Tempest the Dolphin, who challenges him to a race across the Green Hill Zone. It directly borders the city of Sunset Heights, and rests just above part of the Marble Zone. The Green Hill Zone is one of several areas of South Island, where Sonic the Hedgehog's adventure first begins.