A project to build the first underwater bridges will cost $25 billion and be completed by 2035.

Norway is known for its fjords, and while they might be breathtakingly pretty, we imagine they're a pain for the average Norwegian, who needs to resort to car ferries to cross the rocky inlets. That could be why the Norwegian government is planning an ambitious investment to build bridges that float underwater across a number of the country's fjords.

These "submerged floating bridges" sound a lot like tunnels. But the depth of some of Norway's fjords is forcing the Scandinavian country to take a different approach – the bridges sit 100 feet below the water, suspended by floating pontoons. Where applicable, cables could secure the tubes to the fjord floor for even more stability. Two tubes, allowing traffic to flow in each direction, make up the assembly.

That doesn't mean there aren't problems. Inhabitat reports that Norway's system is the first of its kind, and that means the team designing it has some difficult engineering tests to pass. It's not clear how the pontoons will handle rough weather, tidal movement, and currents. So what about a normal bridge, then? The fjords are too wide and too deep, Inhabitat says. Combined with Norway's rocky landscape and occasionally ferocious weather, a typical suspension bridge just wouldn't cut it. The Norwegian Navy also nixed a normal span, because it would prevent its ships from operating in the country's fjords.

We don't know how many of these floating bridges Norway is planning, but the government has earmarked $25 billion for the project, which could be completed by 2035.

Gallery: Norway's underwater traffic solution: a series of tubes

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