Parthenon, Akropolis, Athens, ca. 447-432 B.C.E. Parthenon, Akropolis, Athens, ca. 447-432 B.C.E.

View from inside the east pteroma toward the south (Copyright A. Nicgorski, 1993)

In this view of the Parthenon's front porch, a conservator applies a protective coating to the marble in order to protect it from the corrosive effects of acid rain (a serious problem in Athens today). Acid rain reacts with the surface of the marble to form gypsum, which flakes off easily. It is for this reason that visitors to the Akropolis today are no longer allowed to step on or enter the Parthenon without a special permit.