2. Acropolis of Athens (Greece, Ancient Greek)

While there are many Acropolises in Greece, it is the Acropolis of Athens that is, without question, the most quintessentially important monument that carries the name; indeed, when historians refer to simply “the Acropolis”, it is the one in Athens that is being referenced. Located atop a flat rock rising 150 meters above the city of Athens, its three hectares of standing monuments from the Classic Periclean period (460-430 BCE) include the Parthenon, the Propylea, and the Erechtheum, as well as a few earlier Mycenean edifices such as the Cyclopean Circuit Wall that helped to defend the Acropolis from numerous invasions over the centuries. As the foundational center for Golden Age Athens and its way of thought, the Parthenon is widely considered to be the crucible of democracy and Western culture as we know it.

Hadrian's Arch at the Acropolis, Athens, 2005, marble blackened and corroding from acid rain. Photo by Marcok

In recent decades, as Greece has experienced substantial economic expansion and development, pollutants and heavy vehicle emissions from the booming modern city of Athens have contributed to acid rain in the region. The monumental and sculptural stone of choice for the ancient Greeks, marble, is highly susceptible to heavy surface degradation from even low levels of acid rain. The Parthenon’s magnificent marble relief frieze panels, for instance, have been chemically transformed by acid rain into soft gypsum. As details are lost and the chemical transformation soaks deeper into the marble on these vital monuments, pieces of them have begun to crack and fall off, with structural collapse a possibility in the not-so-distant future. Further complicating the situation is the seismically-active nature of the region, as earthquakes would have a far greater effect on marble constructions that have slowly transformed into gypsum than with unaltered marble.