The massive structure is due to be completed in 2027 and will carry high-speed trains.

Aerial view of Hangzhou Bay Cross-Sea Railway Bridge

The Hangzhou Bay Cross-Sea Railway Bridge is the longest of its kind in the world (Image: Getty)

The world's longest cross-sea high-speed railway bridge has hit a major milestone. The first main tower on the Hangzhou Bay Cross-Sea Railway Bridge in China was successfully topped out on January 16.

The 29.2-kilometre-long superstructure is the world's longest high-speed railway cross-sea bridge currently under construction. When it is finished, expected in 2027, the bridge will hugely bolster connectivity and development in the Yangtze River Delta.

The project is being designed for 350km/h high-speed trains. It is different from the Hangzhou Bay Bridge, which was opened in 2008, in that the original is a road crossing for cars and other vehicles. It is around 35.7 kilometres long. This new structure is being built upstream of the road bridge and is designed for rail traffic only.

Main Tower of the bridge is topped out

The huge structure will see high-speed trains travel over it. (Image: Getty)

The new bridge will be part of the Nantong–Suzhou–Jiaxing–Ningbo high-speed railway, which is a major line designed to better connect cities across the delta.

"As of now, the total investment in the bridge has reached 11.2billion yuan (about 1.61billion U.S. dollars), with 75% of the work completed.

"The bridge is expected to be fully connected by September this year. The entire project is set to be operational by the end of 2027," said Qian Liping, head of the command department of Hangzhou Bay Railway Bridge Project at Shanghai Guotie Engineering and Construction Management Company, Bastille Post reported.

Aerial view of Hangzhou Bay Cross-Sea Rail Bridge

The bridge is due to be completed in 2027 (Image: Getty)

The latest news from around the world Invalid email

We use your sign-up to provide content in ways you've consented to and to improve our understanding of you. This may include adverts from us and 3rd parties based on our understanding. You can unsubscribe at any time. Read our Privacy Policy

“The No. 8 tower’s column consists of lower, middle, and upper sections with two cross beams, and the precision control requirements are extremely high — it’s like ‘millimetre-level carving in the sky’," a  project technical director said, according to Sina Finance.

"Confronted with the harsh offshore conditions, innovations such as large dual-wall steel cofferdams and high-precision synchronous placement technologies have enabled us to build a solid ‘land platform’ at sea and ensure construction is safe, high-quality and efficient.”