The ancient Kanayama Megaliths are extraordinary in their complexity. Across three sites, the solar observatories accurately measure not only solstices and equinoxes but also leap years.

But they would have been left hidden in the forest if it weren't for two people who stumbled upon some strange etchings in the stones.

Without any scientific background, Yoshiki Kobayashi and Shiho Tokuda set out to understand how three of the the world's most sophisticated solar observatories worked.