Nuraghe Santu Antine, also known as 'Sa domo de su re' ('The house of the king') is an ancient megalithic edifice built by the Nuragic Civilization in Torralba, one of the largest in Sardinia. It is located in the centre of the Cabu Abbas plain. The main structure was built around the 19-18th century BC, and the other parts of the nuraghe date back to the 17th–15th century BC. The main tower originally reached a height of 23–24 metres and contains three tholoi chambers on top of each other. The central tower with diameter of 15 metres is 17 metres high. Santu Antine is made of huge basalt blocks. It has three floors. The top floor is now gone. Some 27 meters long corridors built with the corbel arch technique can be observed inside of the Nuraghe, superimposed on two floors, the Nuraghe was provided with three wells.
References:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.