Plans got underway to rebuild this important shrine in 449 B.C. With architect Kallikrates at the helm, the temple was to be a simple Ionic shrine, made of Pentellic marble, and included a prostyle porch with four columns on the front and back. It also was adorned with a sculptural frieze all around, as was customary in Greek temple construction. However, something delayed the construction, and it was not completed until around 420 B.C., built with Poros limestone and faced with marble. It was also surrounded by a sort of guardrail or parapet that would have kept Athenians and other visitors from falling off the Acropolis. This fortification was decorated with relief sculptures depicting various presentations of Nike.