"Hulao Pass", a pass in ancient Chinese legends, was built between two steep cliffs. It has a solid city wall dozens of feet high and a heavy city gate made of metal. Bricks were used to build strong battlements and watchtowers on the towers. In front of the city wall, there is a deep ditch that is manually dug and dozens of feet wide, and flows into the water from the nearby river. To enter Hulao Pass, you can only use the lever-controlled rappelling bridge in front of the city gate.