China has always been ambitious in engineering. More than 2,000 years after the first emperor built the Great Wall, modern Chinese are now planning to build the "great tunnel." The project, to run along the nation's east coast, will be the longest in the world.

The 123-kilometer (76.43-mile) tunnel, which would be more than twice the length of the Channel Tunnel that connects the U.K. and France, will run between the coastal cities of Dalian and Yantai, the Telegraph reported on Sunday.

“Work could begin as early as 2015 or 2016,” said Wang Mengshu, an expert at the Chinese Academy of Engineering, speaking to the China Daily. The tunnel will shorten the journey between the two cities by 1,280 kilometers and form a vital link in a high-speed rail line that connects the cold, northern parts of the country to the tropical island of Hainan, a popular tourism destination in the south.

The sea tunnel, which will reportedly cost $40.5 billion, will include three passageways – one for cars, one for trains and the last for maintenance – all drilled through hard rock 100 feet below the seabed. Vertical shafts will also be dug on islands along the route to provide ventilation.

The tunnel will have to go through an earthquake-prone area, where a 7.5-magnitude earthquake killed hundreds of thousands in the nearby city of Tangshan in 1976, one of the deadliest in China’s history. Experts caution that excavation work for the tunnel needs to be carried out carefully.

“The government is being cautious about the project,” said a researcher on the tunnel at East Shandong University, who asked not to be named, according to the Telegraph. “We proposed this idea of a tunnel 20 years ago and many research teams have been looking at it since."

Chinese researchers have formed a special group to study the Channel Tunnel in preparation for China’s own tunnel project, the researcher said, and have learned some construction techniques as well as ways of financing the undersea tunnel on the Chinese coast.