Øresund Bridge

Supporting both cars and trains as they pass between Denmark and the southern tip of Sweden, the Øresund Bridge (or Øresundsbron, as it is nicknamed in a mishmash of Swedish and Danish), transitions from bridge to tunnel as the road and railway dips beneath the waves. 

The passenger travel connection was completed in 1999, connecting the Swedish city of Malmö to the Danish metropolis of Copenhagen. While building a bridge over the Øresund Strait was not a huge challenge in itself, doing so without interfering with the air traffic above or the shipping traffic on the water seemed almost impossible. Building a suspension bridge tall enough to allow ships to pass beneath it would prevent the busy Copenhagen Airport nearby from functioning. A bridge built any lower would have halted ship traffic. The simple yet unusual solution was a bridge that would descend beneath the waves halfway across the strait.

A man-made island known as Peberholm was built to support the transition point and a tunnel was dug beneath the strait on the Danish end (known independently as the Drogden Tunnel). On the Swedish side, the sweeping suspension bridge was constructed to slowly slope right into the water, making it look from the outside as if the bridge gives up and curves into nothingness.

Today the bridge is the longest automobile and rail bridge in Europe, despite being half-tunnel (the people making such distinctions do not like to be discriminatory). With an estimated 17,000 cars passing over and under the Øresund Strait each day, this span brings a newly literal meaning to the phrase "bridge and tunnel."