The document discusses the Classical period in world history, which ran from around 1000/800 BCE to 500/600 CE. Some key developments during this period included the formation and expansion of major civilizations like China, India, Persia, and the Mediterranean. These classical civilizations established population centers with tens of millions of people, utilized iron technology, and had more contacts with each other than earlier river valley societies through entities like the Phoenicians. The classical period thus saw the emergence of larger, more interconnected civilizations that built upon earlier achievements.