the nebra disk

https://archive.org/details/NebraSkyDisk

It was found by chance 

The Nebra sky disk is a bronze disk of around 30 centimeters (12 in) diameter and a weight of 2.2 kilograms (4.9 lb), with a blue-green patina and inlaid with gold symbols. These are interpreted generally as a sun or full moon, a lunar crescent, and stars (including a cluster interpreted as the Pleiades). Two golden arcs along the sides, marking the angle between the solstices, were added later. A final addition was another arc at the bottom surrounded with multiple strokes (of uncertain meaning, variously interpreted as a Solar Barge with numerous oars, as the Milky Way, or as a rainbow).

The disk is attributed to a site near Nebra, Saxony-Anhalt, in Germany, and associatively dated to c. 1600 BC. It has been associated with the Bronze Age Unetice culture.The disk is unlike any known artistic style from the period.

The Nebra sky disk features the oldest concrete depiction of the cosmos worldwide. In June 2013 it was included in the UNESCO Memory of the World Register and termed "one of the most important archaeological finds of the twentieth century.