Tsarevets is a medieval stronghold located on a hill with the same name in Veliko Tarnovo in northern Bulgaria. It served as the Second Bulgarian Empire's primary fortress and strongest bulwark between 1185 and 1393, housing the royal and the patriarchal palaces, and it is also a popular tourist attraction.
The hill has evidence of human presence from the 2nd millennium BC and was settled in the 4th century. After the Bulgarian Rebellion, it became the empire's key fortress, comparable to Rome and Constantinople. In 1393, it fell to Ottoman forces, marking the Bulgarian Empire's demise.
The fortress has three entrances, with a central complex featuring a throne hall, castle church, and king's chamber. Restoration started in 1930 and was completed in 1981. The stronghold, surrounded by thick walls and three gates, housed kings Petar, Asen, Kaloyan, and Ivan Asen II. The palace complex included a fortified wall, towers, and entrances. The patriarchate, at the hill's top, has the Cathedral of the Ascension of the Lord.
Baldwin's Tower, a modern reconstruction in the southeastern part, commemorates Latin Emperor Baldwin I's death. During the Middle Ages, the hill had residential buildings, workshops, churches, and monasteries. Archaeologists found 400 buildings, 22 churches, and 4 monasteries. Execution Rock, where traitors were pushed into the Yantra River, is also located here; Patriarch Joachim was executed in 1300.
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.