Brazilian archaeologists have discovered an Stonehenge-like stone structure in the Amazon:
A total of 127 large blocks of stone were found driven into the ground on top of a hill. ... Well preserved and each weighing several tons, the stones were arranged upright and evenly spaced.
What impressed researchers was the sophistication of the construction. The stones appear to have been laid out to help pinpoint the winter solstice, when the sun is at its lowest in the sky.