 These incidents appear to have prompted the massive strengthening and expansion of the fortifications in various sites . In some cases , arrangements were also made for the creation of subterranean passages which led to underground cisterns . Tiryns , Midea and Athens expanded their defences with new cyclopean @-@ style walls . The extension program in Mycenae almost doubled the fortified area of the citadel . To this phase of extension belongs the impressive Lion Gate , the main entrance into the Mycenaean acropolis . 
