Linking the countries of Sweden and Denmark is the Oresund Bridge which actually comprises a cable-stayed bridge, an artificial island (Peberholm) and a tunnel. The total length is 16km and is split over two levels (a railway is below the road). Marcus Rangell also added:

According to what I’ve read, the island is also a biological experiment to see how nature will develop on the island. Currently a bunch of plants have already spread to the island, some are very rare.

Thanks: Roland, Thomas, breakbeat, jensflorian, Marcus Rangell, Simone, Yann & Martin

The Middelgrunden Offshore Wind Farm consists of 20 large 2MW windmills in the waters just outside of Copenhagen’s harbour. Covering a length of 3.4 kilometres, the curve of the windmills is designed to be a continuation of the super-ellipse formed by the roads of Copenhagen. There’s loads more info and some great pictures on the official website.

Thanks: Marc Armstrong & blumentopf