The Acropolis was both the fortified citadel and state sanctuary of the ancient city of Athens. Although the great building programs of the 5th century B.C. have disturbed or covered many of the earlier remains, there is still a great deal of archaeological evidence attesting to the importance of the Acropolis in all periods of time. In the Late Bronze Age, the Acropolis was surrounded by a massive fortification wall like those at Mycenae and Tiryns in southern Greece. This wall remained in use long after the collapse of Mycenaean civilization, and functioned as the fortifications of the Acropolis for several centuries. By the middle of the 8th century B.C., if not earlier, at least part of the Acropolis had developed into the sanctuary of the goddess Athena, the patron divinity of the city. It is likely that the first temple of Athena Polias was constructed in this period in order to house a wooden cult statue of the goddess. In the 2nd quarter of the 6th century B.C., probably in association with the re-organization of the Panathenaic festival in 566 B.C., there was a burst of architectural and sculptural activity, and the first monumental, stone, Doric temple of Athena is built on the Acropolis. Another monumental temple was built towards the end of the 6th century, and yet another was begun after the Athenian victory over the Persians at Marathon in 490 B.C. However, the Acropolis was captured and destroyed by the Persians 10 years later (in 480 B.C.). Although the Athenians and other Greeks were eventually victorious over their eastern enemies, the Acropolis lay in ruins. In the mid-5th century, the Athenians were persuaded by the statesman Perikles to rebuild the temples on the Acropolis on a grand scale, and it is during the second half of the 5th century B.C. that the most famous buildings on the Acropolis - the Parthenon, the Erechtheion, the Propylaia, and the temple of Athena Nike, were constructed.
In the Hellenistic and Roman periods, many elaborate dedications were set up on the Acropolis by foreign (non-Athenian) rulers, general, and statesmen. While still functioning as a religious center, the Acropolis, in a sense, became a kind of "museum" or "theater of memory" linking the "glory days" of Athens with the new powers of the Hellenistic and, later, Roman world. In 267 A.D. Athens was invaded and partially destroyed by the Heruli from northern Europe. In the aftermath, a new fortification wall was built around the city, running from the Acropolis north to the Library of Hadrian, east for a few hundred meters, and then finally back south towards the North and East Slopes of the Acropolis. (The course of this "Post-Herulian" or Late Roman fortification wall is not completely known on the eastern side, and it is likely that they included part of the South Slope of the Acropolis as well). The Acropolis once again became an important citadel, and the western appoach was strengthened by a new gateway (the so-called Beulé Gate, named after an early archaeologist). The new circuit also secured an important source of water, the Klepsydra, within the fortifications of the Acropolis. Throughout late antiquity and the Middle Age up until the liberation of Greece from the Ottoman Empire in the early 19th century, the Acropolis remained a strategic and well-defended citadel.
Archaeological excavations, and the necessary conservation, study, and publication of the monuments, were begun in the 1830's soon after Greek indepedence, and continue to the present day.
