The Parthian Fortresses of Nisa consist of two tells of Old and New Nisa, indicating the site of one of the earliest and most important cities of the Parthian Empire, a major power from the mid 3rd century BC to the 3rd century AD. They conserve the unexcavated remains of an ancient civilization which skilfully combined its own traditional cultural elements with those of the Hellenistic and Roman west. Archaeological excavations in two parts of the site have revealed richly decorated architecture, illustrative of domestic, state and religious functions. Situated at the crossroads of important commercial and strategic axes, this powerful empire formed a barrier to Roman expansion while serving as an important communication and trading centre between east and west, north and south.Nisa is situated at the crossroads of important commercial and strategic axes. The archaeological remains vividly illustrate the significant interaction of cultural influences from central Asia and from the Mediterranean world.The Parthian Empire was one of the most powerful and influential civilizations of the ancient world, and a brilliant rival of Rome which prevented the expansion of the Roman Empire to the east. Nisa, the capital of the Parthian Empire, is the outstanding symbol of the significance of this imperial power.