It also passes under the sea: China's massive 55-kilometer bridge (photo)

China's Hong Kong-Zhuhai-Macao Bridge is considered one of the largest infrastructure projects built over the sea. With a total length of 55 kilometers, this bridge-tunnel system connects the cities of Hong Kong, Zhuhai, and Macao. According to official data, it is the world's longest bridge-tunnel sea crossing system.

The structure's total 55-kilometer length includes the Hong Kong connecting road, the 29.6-kilometer-long main bridge, and the Zhuhai connecting road. The approximately 42-kilometer journey from the Hong Kong port to the Zhuhai and Macao ports can be covered by car in about 40 minutes.

One of the most notable aspects of the bridge is that a section of it passes under the sea. The main bridge system also includes a 6.7-kilometer-long underwater tunnel. The tunnel runs along the seabed, with its lowest part located 46 meters below sea level.

Two artificial islands have been built to connect the underwater tunnel with the bridge. The tunnel consists of 33 large underwater segments, with each standard segment being 180 meters long, 38 meters wide, and 11 meters high. Their weight is about 80 thousand tons.

The main bridge-tunnel part of the project was initially estimated at 38.1 billion yuan. During construction, costs increased, and later the approved estimate for the main bridge reached nearly 48.1 billion yuan. The total project cost ultimately amounted to about 127 billion yuan, or around 19.1 billion dollars.

Complex engineering solutions were used in the construction of the Hong Kong-Zhuhai-Macao Bridge. Its main bridge, artificial islands, and underwater tunnel together form a massive transportation system connecting three major regions across the sea.