Built of white Pentelic marble in the Doric order from 447-432 BC, the Parthenon dominates the Acropolis of Athens. Erected in the time of Pericles, it was dedicated to Athena Parthenos, the architects being Iktinos and Kallikrates, the master sculptor Phidias. The plan is peripteral octastyle with seventeen columns on the flanks, standing on a krepidoma of three steps. In the interior the eastern cella is supported by an arrangement of double-tiered Doric columns which framed the colossal chryselephantine (gold and ivory) statue of Athena. The smaller western cella used four single storey Ionic columns to support the roof and ceiling structure. The Parthenon is the apex of the High Classical refinement of the Doric order. This is shown in its slender peristyle columns (approximately 5.5 diameters high) with their subtle entasis and a series of optical corrections which are incorporated into the building's composition. The building's sculptural decoration was extraordinarily rich in both pediments, in the ninety two exterior metopes and in the Ionic frieze above the exterior cella walls. This depicted the Panathenaic Procession, the most important religious festival of Athens. In The Stones of Venice, Ruskin writes of the then 'late discoveries of subtle curvature in the Parthenon' ( Works, 10.153) and in The Queen of the Air ( Works, 19) he writes of Athena and the Panathenaic Procession.