1999 – World's Largest Solid Terrain Model

In 2006, a mysterious 900x700m solid terrain model with military facilities was discovered by a German Google Earth user next to the Chinese town of Huangyangtan. It was quickly identified as a 1:500 replica of a disputed area in Tibet between China and India 2400km away, with perfectly matching orientation. Chinese authorities claimed the model was built 7-8 years earlier as a tank training facility. It is unclear whether the right image represents the same model.

Sources:

1. Newswatch (2011) The mystery of Huangyangtan.
2. Left image from regmedia.co.uk, right image from web.duke.edu.