Outside of Syracuse is the most stunning sequence of fortifications, built and enhanced by the fourth and third century tyrants Dionysius, Timoleon, Agathocles and Hieron II — but finally unable to ward off the Romans. The ruins stretch over the upland plain west of Syracuse
while beneath them runs a fantastic array of tunnels
Most interesting are the efforts made, presumably just before the Roman siege of Syracuse in 213, to force catapults to keep their distance form the fort: a combination of ditches (which the tunnels allow the defenders to clear of any stuff the attackers throw in) and defensive catapults, set on 40ft towers so that they could fire over the ditches to the location of the enemy catapults. Here is the view from the catapult screen over the ditches:
The gate to the north of the fort is also distinguished by some interesting calculations as to how best to defend a gate — and it would have made a pretty impressive entry way for those traveling to Syracuse — an impression reinforced by the continuous wall that ran for another 3.5 miles:
It was in this same area that the Athenians set out to besiege Syracuse and found themselves instead becoming the besieged.