China is about to open the world's longest sea bridge. It cost $20 billion and is 20 times longer than the Golden Gate Bridge.

The $20 billion structure is 20 times longer than the Golden Gate Bridge.

The title of world's largest sea bridge previously belonged to the Qingdao Jiaozhou Bay Bridge, which stretches 26.3 miles.

The Hong Kong-Zhuhai-Macau Bridge is designed to last for more than a century, and has the capacity to withstand major storms and earthquakes.

The structure can hold up in the face of 211 mile-an-hour winds. These claims were put to the test in September, when Typhoon Mangkhut swept through Hong Kong, destroying roofs, shattering windows, and toppling trees.

The bridge is made of 420,000 tons of steel — enough to build 60 Eiffel Towers.

The bridge's towers were inspired by three elements: Chinese knots, the Chinese white dolphin, and the mast of a boat.

The bridge's curves are designed to resemble a snake.

A four-mile underwater tunnel connects two artificial islands, which help support the structure.

The tunnel was built below the water to prevent the disruption of shipping lanes. The Greater Bay Area is one the busiest shipping areas in the world, with around 4,000 vessels passing through each day.

After kicking off in 2009, construction was set to finish in 2016, but was delayed due to budget and safety concerns.

Nine workers have died and more than 200 have been injured over the course of construction.

Nineteen workers have also been charged with faking concrete test reports.

Some have questioned the bridge's stability after photos showed its wave-absorbing concrete blocks drifting off into the water.

Authorities said the structure was intended to be partially submerged, though its renderings tell a different story.

Environmentalists fear that construction has threatened the livelihood of the Chinese white dolphin.

The area where the Pearl River meets the South China Sea was once a sanctuary for the species, whose population has declined since construction began.

Officials expect the bridge to cut commute times in half.

Around 40,000 vehicles are expected to use the bridge each day, with shuttle buses running every ten minutes.

The bridge includes a designated merge point, where cars can switch to the appropriate side of the road.

Those in Hong Kong and Macau drive on the left side of the road, while those in mainland China drive on the right.

Chinese president Xi Jinping is expected to attend the bridge's official unveiling on Tuesday.

To cross the bridge, pedestrians and drivers without a permit will have to purchase an $8 to $10 shuttle ticket.

Experts say Hong Kong should expect an influx of tourists from mainland China.