Introduction to the former site of Shimen: Shimen is located at the southern end of Baoxie Road and is now submerged in the Baohe Reservoir. The "Shimen" was excavated during the reign of Emperor Ming of the Han Dynasty (the sixth year of Yongping in the Eastern Han Dynasty). It was built to connect the Baoxie plank road. The tunnel is 13.6 meters long, 4.2 meters wide, with the south entrance 3.45 meters high and the north entrance 3.75 meters high. It was hewn using the primitive technology of "fire and water" in ancient my country. It is the earliest artificial tunnel open to traffic in the world and is a valuable material for studying the history of transportation in ancient my country.