The Temple of Neptune was erected on the Poreč forum in the 1st century. It is thought to be the biggest in Istria, although only a portion of its walls and the foundations have been preserved.
During the Antiquity, Poreč as well as all Roman towns, had a forum, the main town square known today as Marafor, and a Capitoline temple facing it. It was believed that the temple was dedicated to God Mars in light of interpreting the Marafor as the Martis forum i.e. the forum of Mars. To the north-west, also in the near vicinity of the former forum, are the remains of the Large Temple dedicated to Neptune, the god of the sea. There are some who interpret the remains as a holy ground surrounding the Capitoline from three sides. The temple, dated to the 1st century, is the biggest in Istria in spite of only a portion of its wall and foundations being preserved.
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.