Aqueduct Veluwemeer

Driving down the N302 highway near the Dutch city of Harderwijk, your car will pass under an orange bridge, which appears to be intended for cars or trains. But this is no ordinary bridge: instead of containing a paved road or train tracks, the passageway actually holds a 10-foot-deep canal that allows boats to cross over the highway.

While people normally think of bridges as roads that cross over water, Aqueduct Veluwemeer is the exact inverse—it’s water that crosses over a road. As N302 traverses from Harderwijk on the mainland of the Netherlands to the island province of Flevoland, the highway briefly dips below Lake Veluwemeer to allow small ships and sailboats to cross over it.

Brilliantly engineered to prevent water from spilling onto the road, Aqueduct Veluwemeer uses 22,000 cubic meters of concrete to support the weight of the water above the cars. The aqueduct also uses steel sheet piling to prevent sediment from bleeding onto the highway.

While drawbridges, ferries, and tunnels are more common options for these situations, the engineers of the project decided against them when building the road from 1998 to 2002. Since the N302 is a major road that's used by 28,000 cars per day, stopping the flow of traffic with a drawbridge or a ferry terminal would be a road congestion nightmare. And tunneling across the 2,000-foot gap wasn't chosen because it would be far more expensive than the $61 million price tag of the aqueduct.

In the end, the unique aqueduct design was a cost-effective way for the two-lane highway’s traffic to flow unencumbered while also allowing boat passengers to pass freely at all times of day.