Wanning Bridge, commonly known as the Backdoor Bridge, is named after its location outside of Di'anmen (also known as the Backdoor). It spans the Tonghui River (now the Yu River) from north to south, serving as a node where the two major cultural axes of Beijing's central axis and the Grand Canal cultural belt intersect. It is an extremely precious and important historical and cultural landmark in the ancient Beijing.

Wanning Bridge is a water gate bridge, and the Chengqing Upper Water Gate under the bridge (also known as Haizi Lock) is the last lock gate for barges to enter the end of the Grand Canal. The wooden plank bridge (later changed to a stone bridge after the Ming Dynasty) on the water gate is also the first bridge that barges pass through when leaving the Jishuitan Wharf. The road connected by the bridge is not only the central axis of the Yuan Dynasty, but also a major north-south transportation artery. The transportation of goods gathered along the Haizi coast flows in and out of the city through this area, forming the market pattern where “the palace in the front while the market in the back” in the Yuan Dynasty. Additionally, the commercial activities were very prosperous there at that time.

Nowadays, Wanning Bridge, as a node and hub of the Beijing Central Axis and the Grand Canal World Heritage Site, is an extremely precious historical and cultural landmark of Beijing. It is also a rare cultural relic that has been preserved from the Yuan Dynasty to the present day, thus its historical and cultural value is self-evident.