China opened the Shenzhen-Zhongshan transportation line, a system of tunnels and bridges across the sea in Guangdong Province. This not only connected 2 cities on opposite banks of the Pearl River estuary, but also set as many as 10 world records. The river delta where it flows into the South China Sea is one of the most densely populated areas in the world. It covers Hong Kong, Macau and 9 cities in Guangdong province, which are separated by a wide expanse of water. Therefore, moving around the region is a big challenge. The Shenzhen-Zhongshan line is designed to remedy this. It stretches 24 kilometers and includes an underwater tunnel between 2 artificial islands and a bridge between cities on both sides of the river. This infrastructure reduces a 2-hour journey to 30 minutes. The bridge consists of 8 lanes and can be traveled at speeds of up to 100 km/h. The tunnel section is equipped with innovative safety systems, including robotic patrols and color-coded light systems for evacuation in case of emergency. This infrastructure will be a key element in facilitating travel in densely populated areas, and a transportation link to the world's longest Hong Kong-Zhuhai-Macau Sea Bridge. The new line has set records such as the longest span for a suspension bridge, the highest bridge deck, the longest underwater tunnel and other unique achievements. It is also the world's first underwater interchange between expressways and airports.