Greek chariots were made to be drawn by two horses attached to a central pole. If two additional horses were added, they were attached on each side of the main pair by a single bar or "trace" fastened to the front or "prow" of the chariot, as may be seen on two prize vases in the British Museum from the Panathenaic Games at Athens, Greece, in which the driver is seated with feet resting on a board hanging down in front close to the legs of the horses. The biga itself consists of a seat resting on the axle, with a rail at each side to protect the driver from the wheels. Greek chariots appear to have lacked any other attachment for the horses, which would have made turning difficult.