In his first-hand account of the Gallic Wars (Commentarii de Bello Gallico), Julius Caesar observes that the Gallic people have a moon- based calendar, and that the big event for them was what astronomers now call the Lunar Standstill, which occurs every 18.6 years. Lunar Standstills are marked in several ancient cultures (including sites in Colorado and Ohio), usually by standing stones that indicate the point where the moon seems to rise and set in the same place, instead of rising in one place and appearing to move across the sky to set in another. Now a German scholar, Dr Allard Mees, a researcher at the Römisch-Germanischen Zentralmuseum in Mainz, has discovered evidence to back Caesar’s observation: a huge royal tomb that functions as a lunar calendar and that preserves a map of the sky at Midsummer 618 BC, the presumed date of the burial.