In Greek temples the shafts of the columns not only tapered considerably, but the vertical lines of an entire building inclined to imaginary points determined by the intersection of lines following the inclination of the end columns. The mass was thus in the form of the frustum of a pyramid, being intentionally so designed to bind the parts of the building together in a manner to withstand effectually the oscillation caused by earthquakes, which occur frequently in this region. The city of Athens contained numerous examples of each of these orders, and a brief account of the buildings of that city will be the best means of showing their principal characteristics. The city proper, in which were the chief temples, was built upon a rocky hill rising from the valley of the Illysus, lying between the mountain-chains of Pentelicus and Hymettus, and situated about five miles from the port of Phalerum, on the Gulf of Ægina. This Acropolis (rock city) is approached by a broad flight of stairs leading to the Propylæum, or outer gate, with high pedestals on each side which were formerly surmounted by equestrian statues. The Propylæum is composed of a porch of six Doric columns, giving access to a large vestibule flanked by two outer halls. This vestibule is divided by a flight of steps, placed between six Ionic columns on pedestals, supporting nine marble beams or architraves which carry the weight of the roof. Beyond is a second porch, opening on the plateau of the Acropolis by means of five doors of different proportions. The lintel of the central or largest door measures 23 feet, while the architraves are 17 feet in length and of single stones. The Athenians prided themselves greatly upon the vestibule of the Propylæum, and believed Pericles, by whose direction the building was erected, to have been divinely inspired. The details and proportions of the two orders here combined are of great beauty, and show the most refined study. From the farther porch, the Parthenon (meaning in Greek, virgin), or temple of Minerva, is seen to the right, exhibiting a fine perspective view of its North and West elevations. The temple is raised upon a platform surrounded by steps, and is rectangular in form, composed of a cella, or oblong room, surrounded by an open portico. It measures 228 by 101 feet, having eight Doric columns on the front and seventeen on the flank, inclusive of the corner ones. Ictinus and Callicrates were the architects, under the general supervision of Phidias, who designed the gold and ivory figure of Minerva within. The Doric is of the hexametric order, having an approximate proportion of six diameters of the column to its height.