Here is a keyframe I did for the Artstation "Ancient Civilizations: Lost & Found" challenge. I tried to focus on storytelling.
The storyline is based on the hollow earth theory (alike "Journey to the center of the Earth").
A group of private explorers (a mix of scientists and mercenaries) finds a way in (a remote cave in Iceland) and explores an uncharted vast jungle. They encounter members of a matriarchal society, sharing some similarities with the aztecs.