Apollonia, known in the Early Islamic period as Arsuf and in the Crusader Kingdom of Jerusalem as Arsur, was an ancient city on the Mediterranean coast of today's Israel. Founded by the Phoenicians during the Persian period in the late sixth century BCE, it was inhabited continuously until the Crusader period, through the Hellenistic, Roman, and Byzantine periods, during the latter being renamed to Sozusa. It was situated on a sandy area ending towards the sea with a cliff.
It fell to the Muslims in 640, was fortified against Byzantine attacks and became known as Arsuf. In 1101 it was conquered by the Crusader Kingdom of Jerusalem, and was a strategically important stronghold in the Third Crusade, during which the Battle of Arsuf (1191) was fought nearby. The fortified city and the castle fell to the Mamluks in 1265, when both were completely destroyed.
The site of Apollonia–Arsuf was excavated in the 1990s and opened for visitors as Apollonia National Park in 2002. The above-ground remains before the excavations included the medieval city wall and moat, enclosing an area of about 90 dunam, a Crusader castle with a double-wall system with an area of about 4 dunam, a port with built jetties and a sheltered anchorage, protected by a sandstone reef.
Large amounts of pottery were recovered in the area surrounding the city, mostly of the Byzantine and early Islamic period, indicating that the city extended significantly beyond its old walls in the 7th century. A large Roman-era villa maritima was uncovered to the south of the site.
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.