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

Ploughed into the Australian outback in 1998 (by persons still unknown), the Marree man is a 4km figure of an aboriginal. It’s faded into the desert quite a bit now but the shape (and size!) is still quite apparent. Wikipedia says that it was probably created using GPS and earthmoving equipment. There’s a good page here which discusses the possible reasons for creating the artwork.

Many thanks to Ken Mortimer, who it seems was the only person to submit this!