The location of the Waijinshui Bridge is in strict correspondence with the five arch gates of the Tiananmen Tower and the south gate of the Imperial Ancestral Temple and the Altar of Land and Grain. The layout of the bridge, the width of the bridge deck, the form of the capital and the decorative details all reflect the principle of "selecting the middle". As the leading area to the imperial city of the Ming and Qing Dynasties, the Waijinshui Bridge was the only way from the imperial city to the southern suburbs for sacrifice in the Ming and Qing Dynasties. It is also the ceremonial space for major national celebrations today, and it has always assumed an important ceremonial function. The Waijinshui Bridge is located on the Waijinshui River on the south side of Tiananmen. The bridge body is located opposite to the arch gate of the tower, and the distance between the bridges is basically the same. They are symmetrically distributed along the central axis of Beijing. The Waijinshui Bridge is shaped like a jade belt, and it is combined with the Tiananmen Tower to form a symbolic ceremonial space and form. The five bridges of the Waijinshui Bridge are basically the same in shape. They are all three-arch arch-style white marble bridges. The plane is in the shape of a "工" character with a narrow middle and wide ends. The shape is unique, but the scale and decorative details are different. The architectural level decreases from the middle to the sides. The Outer Golden Water Bridge corresponds to the Inner Golden Water Bridge in front of the Taihe Gate of the Forbidden City. It has played an important ceremonial function since the Ming Dynasty. The bridge in the middle is called the Imperial Road Bridge, which was used exclusively by the emperor during the Ming and Qing dynasties. The left and right sides of the Imperial Road Bridge are the Prince Bridges, which are used by the princes of the imperial clan. The two ends are the Grade Bridges, which are used by civil and military officials above the third grade. The bridges corresponding to the Imperial Ancestral Temple and the Altar of Land and Grain are called the Gongsheng Bridges. Today, the Outer Golden Water Bridge is still the main passage connecting the Forbidden City and Tiananmen Square. The Outer Golden Water Bridge was first built in the 15th year of the Yongle reign of the Ming Dynasty (1417). There were only three bridges at first. After the reconstruction in the first year of the Chenghua reign of the Ming Dynasty (1465), the number increased to seven. The existing bridge was rebuilt in the 29th year of the Kangxi reign of the Qing Dynasty (1690).