http://agathe.gr/overview/the_site_before_excavation.html
The Site before Excavation The Agora lies on sloping ground northwest of the Acropolis, below and east of the extraordinarily well-preserved Doric temple of Hephaistos, popularly known as the “Theseion” ... The other ancient remains were not so well preserved, however, and their ruins lay as much as 8 meters below the modern surface, covered from the 10th century by an extensive neighborhood of private houses. The houses were repeatedly rebuilt, after successive invasions by Franks, Ottomans, and Venetians. The last destruction occurred in 1826, the result of a siege of the Acropolis during the Greek War of Independence. Once again the neighborhood was totally rebuilt, and only limited archaeological excavation was possible. ... Except for these scattered and limited attempts, the remains of the center of ancient Athens lay deeply buried, inaccessible, and largely forgotten.