Which key development that occurred globally during the classical era was?

During the classical era, one key development was the establishment and expansion of trade networks, which facilitated cultural exchange and economic interaction across vast distances. The Silk Road, for example, connected the East and West, allowing for the exchange of goods, ideas, and technologies. This period also saw the rise of powerful empires, such as Rome and Han China, which further integrated diverse cultures and regions through trade, diplomacy, and military conquests. Such interactions laid the groundwork for future global connections and cultural diffusion.