The rescue archaeology soon extended over a large number of graves. The total is not known for sure. Numbers vary from a mere 600 to as many as 60,000. Part of the problem is that over such a length of time graves were destroyed to make way for others, or were placed over others. A few general observations can be made. The earliest cemetery was placed further inland near the center of Ierissos, while the later were more toward the sea., and were aligned pointing to sea. Currently a number of chronological work areas are distinguished, the two main ones being the cemetery of Akanthos, and the medieval cemetery of Ierissos, discovered in 1984. The first contains tombs ranging in time from the Proto-Geometric Period through the abandonment, with the most from the classical centuries, the 5th and 4th BCE. The second contains the graves of mediaeval Ierissos, from the founding of the Kolovou Monastery on the hill in 883 CE, which made use of Greek and Slavic texts, to the 12th century CE, judging by the coins. The fact that some coins date from the 6th century suggests that the site was not entirely abandoned.