The early Chinese people knew there were other tribes of people to the north. But they did not know there were other ancient civilizations in other parts of the world. The Chinese were isolated by their many natural barriers.
To the east and south, China borders two seas - the China Sea and the Yellow Sea. Although these bodies of water provided food and water routes for trade, both seas are located in the Pacific Ocean. The Pacific Ocean is a pretty big place, and few of the early Chinese mariners attempted to explore the Pacific in the early days of China's development.
A huge mountain range called the Himalayan mountains ran along China's border. China also borders two of the world's most dangerous deserts.
You can see why China was isolated for so many years from the rest of the ancient world!