An important part of the defensive system was the manner of entrance to the city from the outside. City gates were protected with every possible care. In prehistoric days the Mycenaean builders of Tiryns, in the Argolid, relied for safety on long passageways between towering stretches of wall, with doors blocking the passage at intervals. Tiryns continues to be one of the most spectacular sites in all Greece. Spring 1930 The same system was sometimes followed in early classical times. The curious wall which blocks the pass between Athens and Eleusis, dating perhaps from the seventh or eighth century, is penetrated by a series of narrow passages which curve through the thickness of the wall in arcs of a full quarter-circle. It has been conjectured that this unusual system was devised especially against chariots or cavalry. 9