RECHNITZ, AUSTRIA—Aerial photographs have led archaeologists in eastern Austria to concentric circular trenches dating to the Neolithic period. The trenches were surrounded by wooden poles, and defensive walls with multiple entrances were found inside the approximately 12-foot-deep trenches. “Such circular trenches are always positioned on a gentle slope, in order to give a clear view of the sky for the observation of the heavenly bodies,” archaeologist Franz Sauer told The Local. The circular earthworks may have been used as a calendar and a ritual space.