The ancient city of Bailu Rizhio, also known as the City of the Sky, is a 100 endangered historical monument in the world. The ancient city was built 2,500 years ago, on a mountaintop with cliffs on all sides, connected to the outside by a narrow pedestrian bridge. From a distance, it looks like a castle in the sky, so it is called the City of the Sky. The ancient city is located 120 kilometers north of Rome. From Rome to the Sky City, you can take the train, which takes about an hour and a half. From the parking lot of the Sky City, it takes about 40 minutes to walk to the ancient city, 1 hour to visit the ancient city, 40 minutes to return, it is recommended to play for 2 and a half hours. There are many people who come to the ancient city in summer. When they go, they encounter a group of Italian students who are led by the teacher downstream the ancient city. After November, April is the off-season for tourism in the ancient city. There are only 8 households in the ancient city, and there are few people in ordinary times. In summer, the permanent population is about 200 people due to the peak tourist season. The ancient city has shops, coffee shops and restaurants. The ancient city is well protected and medieval style is worth a visit.