Fawcett does find Z, five days after leaving the Kalopalo, right at Kuhikugu where they expected. It’s a mandala on the floor of the all-consuming forest.
The Xinguanos liked their buildings sturdy, back when they had buildings, and many have resisted collapse. Everything’s covered in green. The only clean stone is the light well in the central temple, which turns out to lead to the center of the earth.
“Is that where they all disappeared to?” asks his son.
But Fawcett is already scrambling over the edge, hands shaking, headfirst into this perfect manifestation of the fear of the unknown.