The world’s longest sea crossing connecting Hong Kong with Macau and Zhuhai opened this week in China. The unusual bridge cum tunnel system consist of a series of three cable-stayed bridges and one undersea tunnel, as well as two artificial islands for a total length of 55 km.

The largest part of the crossing is the 30-km-long Main Bridge, which is actually a bridge and a 6.7 km undersea tunnel that dips beneath the Pearl River Estuary and emerges at the other end just before the Hong Kong border. The undersea tunnel was built to avoid disrupting shipping lanes. The route then continues over a 9.4-km-long viaduct and ends at Chek Lap Kok, the island where Hong Kong International Airport is located.

The Hong Kong-Zhuhai-Macau Bridge lit up in Hong Kong.