Brazil's 1,000-year-old calendar
22 December 2015 Last updated at 16:39 GMT
A pre-colonial astrological observatory in the Brazilian rainforest was built to be aligned to the sunrise on the December solstice - which falls on 22 December in 2015.
The so-called Amazonian Stonehenge, in Brazil's northern-most state Amapa, is believed to have been constructed over 1,000 years ago.
But the site was only discovered in 2006, and plans are now are afoot to make it a national archaeological heritage park.
Video Journalist: Gibby Zobel
More video features from the BBC News Magazine