Kaliakra is a long and narrow headland in the Southern Dobruja region of the northern Bulgarian Black Sea Coast, located 12 km east of Kavarna and 60 km northeast of Varna. The coast is steep with vertical cliffs reaching 70 m down to the sea.
In 4th century BC a settlement called Tirrisis was founded bearing the name of a local Thracian tribe. In Roman times the fortress rapidly grew – lots of public buildings and facilities were built. There were plumbing system, churches, public baths (Roman thermes), fortification walls most of which can still be seen today. The cape became a strong Bulgarian fortress and flourished in the second half of the 14th century as a capital of the Dobrotitsa dukedom. It was a powerful medieval town minting its own coins. The fortress declined when it was conquered by The Ottoman Empire.
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.