The Palace of Omurtag is an archaeological site in northeastern Bulgaria dating to Late Antiquity and the Early Middle Ages located near the village of Han Krum in Shumen Province. The site has been pinpointed as the location of a fort and palace of Omurtag, ruler (kanasybigi) of the First Bulgarian Empire in 815–831, as mentioned in the Chatalar Inscription of 822. Earlier structures in the vicinity of the fortress have been identified as the Arian episcopal see of a Gothic bishop.
The main feature of the archaeological site is the early-9th-century Bulgarian fortified rampart with Omurtag's palace within its limits.
The earliest ruins at the Palace of Omurtag site include four churches, two of which built on top of each other; a bath; and fortified walls, all dating to Late Antiquity (roughly 250–650 CE). Three of the churches and the bath lie outside the medieval fortification, while one of the churches and the traces of ancient walls have been excavated within its limits.
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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.