The ruins of ancient Sparta lie north of the modern city. It was a prominent city-state in Laconia in ancient Greece. Around 650 BC, it rose to become the dominant military land-power in ancient Greece.
Given its military pre-eminence, Sparta was recognized as the leading force of the unified Greek military during the Greco-Persian Wars, in rivalry with the rising naval power of Athens. Sparta was the principal enemy of Athens during the Peloponnesian War (431–404 BC), from which it emerged victorious after the Battle of Aegospotami. The decisive Battle of Leuctra against Thebes in 371 BC ended the Spartan hegemony, although the city-state maintained its political independence until its forced integration into the Achaean League in 192 BC. The city nevertheless recovered much autonomy after the Roman conquest of Greece in 146 BC and prospered during the Roman Empire, as its antiquarian customs attracted many Roman tourists. However, Sparta was sacked in 396 AD by the Visigothic king Alaric, and underwent a long period of decline, especially in the Middle Ages, when many of its citizens moved to Mystras.
Entering by the South Gate of the Acropolis, known as Lakedaemonia, there is the Rotunda, the Theatre and the Temple of Athena Chalkioikos to the West. Exiting the Acropolis by the North Gate there are the remains of the earliest ancient walls, the Heroon and the Altar of Lycourgos, whereas to the East there is the Sanctuary of Artemis Orthia. To the North is the Monastic Church of Osios Nikonas (10th century).
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.