The gorge area was inhabited at least as early as the Iron Age, probably by the Dobunni tribe. In Leigh Woods above Nightingale Valley, a steep dry valley beside the suspension bridge, is Stokeleigh Camp, one of three Iron Age hill forts in the area. Stokeleigh was occupied from 3BC to 1AD, and was also used in the Middle Ages. The camp was protected on two sides by the cliff faces of the gorge and Nightingale Valley, and was also protected by earthworks, and is now a scheduled ancient monument. A second hill fort was situated across Nightingale Valley, but has since been built on, and bridge road cuts through it. The third hill fort was situated on the opposite side of the gorge, in what is now observatory green. Archaeology, plus the configuration of the three forts, suggest they played a role in defending the gorge.