شاهنشاهی ساسانی — واپسین امپراتوری بزرگ ایران (۲۲۴–۶۵۱ میلادی)
The Sassanid (Sasanian) Empire (224–651 AD) was the fourth Iranian empire and the second to be called the Persian Empire. Founded by Ardashir I after he overthrew the Parthian dynasty, the Sassanids self-consciously positioned themselves as heirs of the Achaemenid Empire and restorers of Persian glory.
At its height, the Sassanid Empire stretched from Mesopotamia to Bactria, from Arabia to the Caucasus — a superpower that fought Rome and Byzantium as equals. Shapur I (r. 240–270) captured the Roman Emperor Valerian — the first and only Roman emperor ever taken prisoner. His relief at Naqsh-e Rostam shows the kneeling emperor.
Sassanid culture produced extraordinary achievements: the magnificent Ctesiphon arch (the world's largest single-span brick vault), stunning rock reliefs, intricate silverwork, silk weaving, and chess. Zoroastrianism was the state religion, with the sacred flame maintained at fire temples. The empire's administrative and cultural legacy profoundly shaped the subsequent Islamic civilization.
The Sassanid Empire ended in 651 AD when the Arab Muslim forces completed their conquest of Persia, killing the last Sassanid king Yazdegerd III. This began the gradual Islamization of Iran over the following centuries.
Ctesiphon was the Sassanid capital near modern Baghdad. Its great iwan (arched hall), Taq Kasra, with a span of 37 meters, was the world's largest single-span brick vault — a marvel of ancient engineering that still partially stands.