One of the factors that contributed to so many geoglyphs being undetected prior to the aid of satallites is their enormous size. According to leading geoglyph scientist Alceu Ranzi, his latest discoveries–five sets of geometric shapes, with circles, squares and lines–can measure more than a mile from one extreme to another.
Because they’ve been so hard to find, the first geoglyphs weren’t discovered until the 1970s. Since then, scientists have been trying to piece together what significance they may have had to ancient Amazonians. What ever the purpose may have been, there’s one thing that is certain: the ancient civilizations of the rainforest were more numerous and sophisticated than previously imagined.
According to a report from Globo, the new marks were only discovered because the jungle coverage had been removed to due to deforestation in the Amazon. These structures are deep, with grooves are as large as 12 meters wide and four deep, but it is believed that they were built when jungle abounded–which would make their construction all the more difficult.
Check the places here (in portuguese)