Introduction to the plank road: The Yimeng Mountain area is famous for its many ridges. The tops of the ridges are mostly flat square hills. From the top of the ridges downwards, there are sharp cliffs surrounding them. The slope below the cliffs ranges from steep to gentle, and the Royal City in the Sky - Ji Wang Gu is the largest Gu among the seventy-two Gu in Yimeng, with a top area of 4 square kilometers. It is the most typical Gu in appearance and the only one inhabited by people, so it is known as the first Gu in Yimeng. Along the cliff plank road built in the scenic area, tourists can enjoy the peaks of Yimeng Mountain and touch the steep cliffs of the Royal City of Heaven with their own hands.