Deep in the wilds of southern Mexico lies a river canyon lined with treacherous cliffs and a jungle so forbidding that this isolated area was one of the last untouched archaeological sites in the world. The first unsettling clues of a lost civilization were found by a group of Italian cave experts setting out simply to chart this remote Chiapas region. Now scientists are ready to risk their own lives in a search for remains of ancient life- and death- lurking high above the Rio La Venta, but long lost to history.

Join NOVA and a team of archaeologists on a breathtaking adventure along rushing rapids, up craggy mountainsides, and into the dusty recesses of dark chambers untouched for nearly a thousand years. Their finds- the sacrificial sites of a legendary Zoque tribe from the time of the Maya- are both disturbing and thrilling: centuries-old cotton cloth, mysterious drawings, remnants of food, fierce jaguar carvings, and the delicate bones of infants whose blood was shed to keep the gods appeased.

Spurred by these artifacts, the team sets off on another exhausting trek, this time through the dense jungle nearby. It’s a journey that will reap rewards on a scale few modern explorers expect to see: the discovery of a previously unknown Mesoamerican city, hidden by hundreds of years of undergrowth. “It’s like being transported to a world that I thought was gone forever,” says expedition leader Giuseppe Orefici in disbelief.