The Biggest Contribution of the Han Dynasty is clearly their INTELLECTUAL Achievements
The Han dynasty made many great accomplishments in the "Intellectual" category of PERSIA (as in the ancient society analyzing strategy, not the nation). It helped to connect people with the creation of the silk road, and greatly contributed to the globalization of China by being the biggest dynasty (Land control wise) in all of China's history. In addition to this, they had such a great influence that they would affect Korea, Mongolia, Vietnam, and most of Central Asia.
The Han dynasty's intellectual achievements have shaped China in monumental ways, such as contributing to the great wall of China, as well as creating the silk road to trade China's silk, a rare and mostly unseen article of merchandise that was never seen outside of China until the silk roads creation.