A 4-kilometer-long floating bridge, which would break the current world record by 2,754 meters, and the first floating tunnel, also 4 km, are among a series of remarkable highway structures, estimated to cost $24.5 billion, planned along more than 1,000 km of Norway’s E39 coastal highway.

Government engineers studying the fixed crossings of seven fjords, which are too wide and deep for conventional structures, say the project is likely to push the boundaries of bridge design well beyond current limits.