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.