The Persian Empire literally: Iran refers to any of a series of imperial dynasties that were centered in the region of Persia (Iran) from the 6th century BC. C., during the reign of Cyrus the Great of the Achaemenid Empire, until the 20th century AD. C. with the Pahlavi dynasty. In 1979, after the Iranian revolution, the Iranian monarchy was replaced by the Islamic Republic. The first dynasty of the Persian Empire was created by the Achaemenids, established by Cyrus II the Great in 550 BC. C. with the conquest of the Median, Lydian and Babylonian empires. It covered much of the ancient world until it was conquered by the Macedonians, led by Alexander the Great. Persepolis is the most famous historical site associated with the Persian Empire in the Achaemenid era and was declared a UNESCO World Heritage Site in 1979. The Persian Empire in the Sassanian era was interrupted by the Muslim conquest of Persia in 651, establishing the Islamic caliphate in the region, and later by the Mongol invasion. The main religion of ancient Persia was Zoroastrianism, but after the 7th century it was slowly replaced by Islam, which reached a majority in the 10th century.
