The main structure of an artificial island — part of the Shenzhen-Zhongshan Link — was completed on Tuesday, marking another milestone for the mega-project, which will open next year.

Linking the eastern and western banks of the estuary of the Pearl River, the project consists of two man-made islands, a sea tunnel and two bridges.

The eastern artificial island is located south of the Shenzhen Baoan International Airport, connecting a passage to the riverside Guangzhou-Shenzhen Expressway on the east and the sea tunnel on the west.

Covering 343,800 square meters, the island is designed to accommodate part of the sea tunnel, rescue docks and power supply facilities, according to Guangdong Provincial Communication Group.

Through the island, vehicles will be able to travel to Huizhou city and Longgang district of Shenzhen to the east, Zhongshan and Zhuhai cities to the west, Guangzhou and Dongguan cities to the north, and Qianhai area in Shenzhen and further to the Hong Kong Special Administrative Region to the south.

The building of the island began in late 2017. Challenges come partly from the requirement that the operations of the nearby riverside Guangzhou-Shenzhen Expressway and the Shenzhen Baoan International Airport should not be affected during construction.

Extreme care was taken to ensure the safety of the expressway, according to Zhang Changliang, director of the department of island-tunnel engineering for the link.

Measuring 24 kilometers in total length, the Shenzhen-Zhongshan Link will shorten travel time between the two cities from one and a half hours to about half an hour, strengthening the connections within the Guangdong-Hong Kong-Macao Greater Bay Area.

It is listed as one of the major engineering projects in the country's 14th Five-Year Plan (2021-25).

Construction of the project started in late 2016. The main structure of the western artificial island has been completed and the tunnel and the bridges have been connected, the company said.