The Seleucid Empire was a vast Hellenistic state that emerged after the death of Alexander the Great in 323 BCE. Founded by Seleucus I Nicator, one of Alexander's generals, the empire stretched from the eastern Mediterranean to parts of present-day Iran and Afghanistan. It was known for its cultural diversity, blending Greek and local traditions, and for its major cities like Antioch and Seleucia. At its height, the Seleucid Empire played a crucial role in trade and cultural exchange between the East and West. However, it faced challenges from rival kingdoms and internal strife, leading to its gradual decline. By the 1st century BCE, the empire fragmented, paving the way for the rise of other powers in the region.