There is some disagreement as to whether this symbol, carved into a hillside in Dorset, dates back to the Iron Age, or is more recent. The Wikipedia article casts doubt on it's ancient origins, About.com does not.

From Wikipedia:

The Cerne Abbas giant, also referred to as the Rude Man or the Rude Giant ("rude" meaning "naked"), is a hill figure of a giant naked man on a hillside near the village of Cerne Abbas, to the north of Dorchester, in Dorset, England. The 55 metre (180 foot) high, 51 metre (167 foot) wide figure is carved into the side of a steep hill, and is best viewed from the opposite side of the valley or from the air. The carving is formed by a trench 30cm (1 foot) wide, and about the same depth, which has been cut through grass and earth into the underlying chalk. In his right hand the giant holds a knobbed club 36.5 metres (120 feet) in length.