It was not until the excavations of the 1930s that many of the relics, reliefs, and clay tablets that offer so much information about Persian life could be studied for the first time. Through archaeological remains, ancient texts, and work by a new generation of historians, a picture can today be built of this remarkable civilization and their capital city. Although the city had been destroyed, the legacy of the Persians survived, even as they mostly remain an enigma to the West and are not nearly as well understood as the Greeks, Romans, or Egyptians. In a sense, the Achaemenid Persian Empire holds some of the most enduring mysteries of ancient civilization. When considering this empire's rulers, the two most often referenced are Xerxes, the leader of the Persian invasion of Greece which caused the heroic sacrifice of the Spartans and their allies at Thermopylae, or Cyrus the Great, the man who created the Persian Empire. But the Persians had another critical ruler sandwiched between them, and Cyrus's accomplishments and Xerxes's defeats would not have been possible without him. That king was Xerxes's own father, Darius I, best known as Darius the Great. Darius I took the throne after the death of Cyrus's son, Cambyses II, and though his reign would not have been possible without the construction of the empire and the administrative groundwork laid by Cyrus the Great before him, Darius proved himself just as worthy of the epithet. Reigning for over 35 years, Darius kept control of the massive Persian Empire despite numerous rebellions and uprisings, and he also managed to implement reforms and improvements that established the empire's golden age. He followed the example of Cyrus before him in his foreign policy and mode of kingship as well, offering tolerance and patience to various cultures and religions, and even treating his enemies fairly in most cases.