The Roman Thermae are a complex of ancient Roman baths in the Black Sea port city of Varna in northeastern Bulgaria. The Roman Thermae are situated in the southeastern part of the modern city, which under the Roman Empire was known as Odessus. The baths were constructed in the late 2nd century AD and rank as the fourth-largest preserved Roman thermae in Europe and the largest in the Balkans.
Ancient Varna, first a Thracian settlement and then an Ancient Greek colony, became part of the Roman Empire in 15 AD and was assigned to the province of Moesia with a certain degree of local autonomy. The Roman baths of Varna were built towards the end of the 2nd century and remained in use for about a hundred years, till the late 3rd century. Coins of Roman emperor Septimius Severus (r. 193–211) have been discovered among the bath ruins. Much later, in the 14th century, the ruins of the Roman Thermae were the site of craftsmen's workshops.
By area, the Roman baths of Varna are the fourth-largest among the preserved thermae in Europe. The thermae are the largest in the Balkan region and the biggest surviving ancient building in what is today Bulgaria.
The Roman Thermae of Varna feature the whole range of facilities including an apodyterium (changing room), a frigidarium (cold pool), a tepidarium (warm pool) and a caldarium (hot pool) as well as a palaestra (a space with social and athletic functions). Heating was provided by means of a hypocaust, an underfloor heating system of pipes.
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.