Discovery of 'calendar' rock carvings from Ancestral Pueblo in US Southwest surpasses 'wildest expectations'
Spiral petroglyphs carved into a canyon wall on the Colorado-Utah border may have been used as a calendar by the Ancestral Pueblo.
TroibNews 
Spiral petroglyphs carved into a canyon wall on the Colorado-Utah border may have been used as a calendar by the Ancestral Pueblo.
