It may seem strange that Kleisthenes, or whoever built the earlier Parthenon, did not at once utilize the Pelasgian wall and boldly pile up his terrace against its support. But it must be remembered that the space between the Parthenon and the Pelasgian wall was very great; an immense amount of _débris_ would be required for the filling up of such a space, and it was probably more economical to build the polygonal supporting-wall nearer to the Parthenon. Anyhow it is quite clear that the polygonal wall was no provisional structure. Its façade shows it was meant to be seen, and that the terrace was meant for permanent use is clear from the fact that it is connected by a flight of steps with the lower terrace under the Pelasgian wall (Fig. 8). It is clear that whoever planned these steps never thought that the lower terrace would be levelled up. Doubtless whoever filled in the terrace to the height of the raised Pelasgian wall believed in like manner that his work was complete. But Kimon thought otherwise. We know for certain that it was he who built the great final wall, the structure that remains to-day, though partly concealed by mediaeval casing Fig. 7 (4). Plutarch[21] tells us that after the battle of Eurymedon (469 B.C.) so much money was raised by the sale of the spoils of the Persians that the people were able to afford to build the south wall. We know also that this wall of Kimon was at least as much a retaining wall to the great terrace as a fortification. For the filling up of the space between the Pelasgian fortification and his own wall Kimon had material sadly ample. He had the _débris_ left by the Persians after the sacking of the Acropolis. The fragments of sculpture and architecture that bear traces of fire are found in the strata marked IV, and there only, for it is these strata only that were laid down after the Persian War[22]. The last courses of ‘Kimon’s wall’ (5) were laid by Perikles, and he it was who finally filled in the terrace to its present level (V). [Illustration: FIG. 8.]