The Unfinished Temple
Dörpfeld, in Athenische Mittheilungen 27 (1902) gives the dimensions of the older Parthenon, the one built of poros blocks as an extension of the substructure, as 33.88 x 76.88 meters. This suggests that the stylobate had the ideal dimensions of 110 x 250 Greek feet of 308.2765 mm., but the actual length was reduced by ½ foot. The important dimension was that of the inner amphiprostyle temple, without columns, which was apparently planned to have the dimensions of 84 x 240 trimmed lesser feeti.e., three near-squares of 80 x 84 feet, with a diagonal of 116 feet. The diagonal was important since it allowed setting the right angles for the corners with great precision. The same two modules of foot were later used for planning the Periclean temple: trimmed lesser feet for the temple itself and Greek feet for the outer colonnade.
When Hill discovered the inner temple in 1912, he considered it to be a separate temple, even though its placement exactly in the midst of the the plan of Parthenon I, its unusual length in relation to the width, and the fact that it had only six columns on the two fronts, should have made him realize that the structure he discovered was nothing but the inner temple of the proto-Parthenon identified earlier by Ross and Dörpfeld. In support of his thesis that the temple discovered by him was a separate structure, Hill could point to the fact that the stylobate as well as the euthynteria were or marble. But the lowest step, the crepis, is of Karrha limestone, and this step is at the same time the highest of the three steps of Parthenon I. Hence Parthenon I and II have a Karrha limestone step in common. It is unusual that a marble temple, which Parthenon II was intended to be, should be surrounded by an outer colonnade of poros limestone, but it would seem that the decision to use marble for the inner temple was not in the original plan. Since a marble colonnade could not rest on a platform of limestone, it was necessary to place additional marble steps upon the original limestone platform of Parthenon I. Hence, although there were two changes in plan during the construction of the Parthenon, the architects tried to accommodate the first change within the scope of the original project by a mere modification, but once it was decided to build the entire temple of Pentelic marble, there was no longer any question of a mere modification. The marble platform had to be laid anew atop the old poros platform. Hence the change of plans from Parthenon I to Parthenon II did not involve an abandonment of the earlier project. The inner temple had been planned in any case, and the only modifications were those required by the change of material from poros to limestone. The decision to use the sturdier Karrha limestone for the stylobate of Parthenon I may have been made due to the experience at Bassai, where the poros stylobate of the temple of Apollo Epikourios began to show cracks from the weight of the the superstructure.