Claustra is a documentary about forgotten archaeological heritage from the period of late antiquity. Although it is as important as the Wall of Hadrian or Danube Limes, this largest Roman building and military system from the second half of 3rd and 4th century located in today's Croatia and Slovenia is still unknown to many. This documentary takes us through parts of Claustra in Croatia and Slovenia and introduces us to its towers, fortifications, walls, explorers as well as fights that took place around it. It seems that the fortification system that was built as a final line of defense, interestingly enough, never served that purpose. Rather, it was used for internal fights of emperors and usurpers. Claustra was produced by Žmergo Association and Ukus Association.