Based on their experience of the Torrid Zone south of Egypt and Libya, the Greek geographers judged it uninhabitable. Symmetry requires that there be an uninhabitable Frigid Zone ("katepsugmenē", "frozen") to the north and reports from there since the time of Homer seemed to confirm it. The edge of the Frigid Zone ought to be as far south from the North Pole in latitude as the Summer Tropic is from the Equator. Strabo gives it as 24°, which may be based on a previous tangent of Pytheas, but he does not say. The Arctic Circle would then be at 66°, accurate to within a degree.