The Claustra Alpium Iuliarum, aka Liburnijski limes or Rimski Zid was a defensive system within the Roman Empire between Italia and Pannonia that protected Italy from possible invasions from the East. It secured the Postojna Gate, the land link between the eastern and western part of the empire, and thus the Claustra represented an inner border defence of the Roman Empire. This section near Studena in Croatia has been cut through by a forest track and is now a cleared rubble and grass ridge.