In the second year of Emperor Kai of Sui Dynasty (582), Daxing City, a new capital, was established in the southeast of Chang 'an City in Han Dynasty. After entering the Tang Dynasty, it was renamed Chang 'an, and it was still the capital, but it was only partially built and expanded to the prosperous Tang Dynasty.

After Zhenguan in Tang Dynasty, Chang 'an Palace was built. In the eighth year of Zhenguan (634), Yong 'an Palace was built on the original highland of Longshou in the northeast of Taiji Palace, and was renamed Daming Palace the following year. After three years of Longshuo (663), it became the main meeting place. Xuanzong also built Xingqing Palace in Fandi Xingqing Square. In addition, in the southeast corner of Chang 'an City in Tang Dynasty, there is also a scenic spot-Qujiang Pool, which is a pioneering work in the ancient urban planning of China.

There were mainly three palaces in Chang 'an in Tang Dynasty, namely Taiji Palace (called Daxing Palace in Sui Dynasty), Daming Palace and Xingqing Palace, which were collectively called "Inner Three Palaces".

1, the east-west width of Taiji Palace1285m, the north-south length1492m, and the area is about1.92km2.. The palace is divided into three areas from south to north: the former dynasty, the later dynasty bedroom and the back garden. The main hall of the former dynasty was Taiji Hall (called Daxing Hall in Sui Dynasty), surrounded by huge palaces surrounded by cloisters, with official offices on the east and west sides. The main hall of the back bedroom is Liang Yi Hall (called Zhonghua Hall in Sui Dynasty), surrounded by halls such as Wanchun Hall, Qian Qiu Hall, Ganlu Hall, Shenlong Hall and Anren Hall. The garden is located in the last part of the palace, with pavilions and ponds. There is Xuanwu Gate on the palace wall in the north, where the famous "Xuanwu Gate Change" took place. Because the Taiji Palace was built by Emperor Wendi of Sui Dynasty, the decoration is relatively simple. After Tang Gaozong ascended the throne, he felt that it was damp here and moved to Daming Palace.

2. Daming Palace is located on the plateau of Longshouyuan in the northeast of Taiji Palace. It is a relatively independent castle overlooking the whole Chang 'an City. Built in the eighth year of Zhenguan (634), this palace was the place where Emperor Tang Gaozong lived and handled state affairs, and was called "Dongnei". Miyagi has a symmetrical central axis pattern. The front of Miyagi is composed of Danfengmen, Hanyuan Temple, Zhengxuan Hall and Chenzi Hall, while the back is composed of the inner courtyard centered on Ethereum, with dozens of halls and pavilions such as Linde Hall, Sanqing Hall, Dafu Hall and Qingsi Hall. The whole Daming Palace is 1.5km wide from east to west, 2.5km long from north to south, and covers an area of about 3.2km 2, making it the largest of the "three palaces".

Xingqing Palace is located in the east of Waiguocheng. This used to be the official residence of Emperor Xuanzong of Tang Dynasty when he was king of Linzi in his early years. In the second year of Kaiyuan (7 14), it was renamed Xingqing Palace. In the 14th year of Kaiyuan (726), it was expanded and merged with the surrounding palaces and temples. Completed in the sixteenth year (728), it was called "Nannei". In the 13th year of Tianbao (754), palace walls and towers were built to form a small castle. At the same time, a waiguo wall was added to build a city between Daming Palace in the north and Furong Garden in the south, which is convenient for the palace people to sneak. Tang Xuanzong and Yang Guifei lived here for a long time. After the prosperous Tang Dynasty, its status was reduced and it became the place for the Empress Dowager and the Empress Dowager.

There are many Buddhist temples in Chang 'an, and Zongzhi Temple, Zhuang Yan Temple, Xingshan Temple and Du Xuan Temple all occupy the whole square. Other famous Jionji (Big Wild Goose Pagoda), Jianfu Temple (Little Wild Goose Pagoda) and Seiryuji also own large areas of land.

There are four ditches in Chang 'an city, namely, Ming Longshou, Qingming, Yong 'an and Caoqu, which introduce tributaries of Weihe River into the city from the southeast and west respectively to provide domestic and environmental water. The first three canals were dug in the third year of Huang Kai in the early Sui Dynasty (583), and the grass canal was dug in the first year of Tang Tianbao (742).

Chang 'an in the Tang Dynasty was the starting point of the Silk Road, connecting China with countries in Central Asia, West Asia and Europe. On the Jilitu Fort outside Anyuanmen, the northernmost gate of the west wall of Chang 'an City, it says "Go west to Anxi for nine thousand miles". This is not the actual mileage, but the journey from Chang 'an to the westernmost point of the motherland, not the "trip to Wan Li". This is a very heroic spirit, as if to encourage people at that time to yearn for the frontier, which reflects the ambition of a powerful nation.