In a quiet corner of the Baltic Sea, a sleepy German holiday island is about to be transformed by one of the largest infrastructure projects in the world.

The island of Fehmarn sits just off the mainland of Germany and is separated from the south coast of Denmark by a 20km stretch of water known as the Fehmarn Belt.

Construction is under way on a tunnel between the two countries that will provide the missing link in a transcontinental highway which will move hundreds of thousands of people a year and generate billions of dollars in revenue.