Before Andy could decipher whether Farah was being playful or snarky, there was the sound of approaching footsteps. Roth, Holland, Rix, Sean, and Darnell were striding toward them. Sean was holding the large video camera and Darnell was carrying a large pack—the portable audio mixer/recorder—and a six-foot boom mike with attached windshield.

“Finally!” Farah cried.

After Holland checked their backpacks to make sure they had emergency overnight supplies should they get separated, he handed out walkie-talkies. “I’ve got them set to channel six,” he said.

Andy took the yellow walkie-talkie and clipped it to the left shoulder strap of his backpack.

Next, Holland went down the line and clipped a carabiner to each of their backpacks. Attached to each was an orange plastic fob, two inches square.

“These are GPS beacons,” Holland said. “Do not, under any circumstances, take them off your backpack. And do not, under any circumstances, take off your backpack.”

Holland glanced over at Rix, who was holding a rugged military-issue iPad. “How are we looking? Do we have a signal?”

Rix turned the tablet toward Holland, revealing eight blinking red dots. “For now we do.”

“Roger that.” Holland turned back to the group. “All right, let’s move out.”

Holland was the first to cross the stream. It was only a foot deep, but the embankment on the opposite side was slippery with mud. It took the ten of them—Libby was staying behind to continue setting up the main camp—several minutes to make their way up the sloping incline.

Holland and Rix pulled out their machetes and began hacking through the wall of green. Andy couldn’t see more than a dozen feet in any direction.

They passed through a second muddy channel, after which the terrain sharply rose, forcing them to pull themselves up with nearby branches and vines. Cala, who was in the worst shape of anyone, needed help from Rix to get up the steep slope.

Once the embankment flattened out, Roth—who along with Cala, Holland, and Farah, was holding a Trimble GPS that had been linked to the lidar scans—said, “The edge of T2 should be just up ahead.”

Andy knew it had been imperative for the ancient civilization to build its city on an elevation above the floodplain. Had they not, each rainy season they would have been inundated by the rising waters of the nearby rivers.

A minute later, Roth, who was wearing a straw cowboy hat and had a red bandanna tied around his neck, glanced down at the LED screen of his GPS and said, “This is it. This is the edge of the city.”