Zavala brushed the dirty walls with his fingers. "You could be right. This looks like dried pond scum."
They climbed back into the fresh air and explored the perimeter of the structure. It was built onto a stone platform that had become the catchall for material floating in the lake. Seeds, probably brought in by birds, had sprouted, and their roots kept the dirt from blowing away Looking straight down into the water at the edge of the island, it was possible to see a stone terrace. Austin kicked off his boots and slipped into the water, swam out a few strokes, and dove.
"This thing is like the tip of an iceberg," he said when he resurfaced. "It was probably a temple on top of a very big pyramid. Can't tell how far it goes."
"Told you we should have brought a submarine," Zavala replied as he gave Austin a hand back onto dry land. "So if what we think is true, and that building is a temple, we're at ground zero. The jaws."
All we have to do is figure out how to get into the gullet."
"Lovely thought. We could try blowing that slab blocking the way"
"Yeah, we could do that, and it might even work But it's not exactly a surgical approach. Our archaeologist friends would never speak to us again. Let's think about it while we look around."
They got back in the plane and taxied to the end of the lake, where they went ashore and made their way inland. The forest was in semidarkness except for the mottled sunlight filtering through the tree canopy. The trees discouraged undergrowth, making for an easy hike on a carpet of leaves. Austin followed a babble of water to its source and stopped where the river they had seen from the air was flanked by stone foundations. The river bed between the foundations was filled with earth and vegetation, but several streams flowed from the substantial reservoir that had built up behind the crude dam and around the old barricade toward the lake. The main course of the river turned abruptly just before it hit the foundations and angled off into the forest. Austin followed the rushing waters away from the reservoir and stopped again at a similar pair of foundations.
"Just as I thought," he said.
Zavala was impressed. "How'd you know these things would be here?"
"Would you believe it if I said I was a dam genius?"
Zavala winced. "Of course I would. Now tell me how you really knew."
Austin picked up a branch, threw it into the river, and watched it disappear from sight in the fastmoving bubble and foam. "You remember how this river looks from the air? I think you said it had more wiggles than a belly dancer. Just before it comes into the lake, it angles off in a perfectly straight line. My first impression was that the section was too straight to be natural. Like. that temple in the center of the lake. Nothing in nature is absolutely perfect. Maybe it was a canal, I thought. You know the Chesapeake and Ohio historical park north above Washington?"
"One of my favorite places for a cheap first date," Zavala said with a smile built of fond memories. "Muy romantico. What's that got to do with anything?"
"Think about that temple. Sometimes it's underwater. Sometimes it isn't."
Austin could almost hear. the gears whirring as Zavala's brilliant mechanical mind processed the information. He slapped his forehead. "Of course. The locks."
Austin cleared a bare spot on the ground and picked up a short stick. He handed it to Zavala. "Be my guest, Professor Z."
Zavala drew a line in the dirt. "This is the Potomac River. You can't move boats up and down, the river because of the rapids and falls, so you cut a canal around the white water. Here." He tapped the ground. "You build a system of gates and sluices to control the water level in the canal one section at a time. Let's see if I'm right." He drew an oval representing the lake. "In its normal state the river comes in here at the top,, fills the flood plain to create the lake, then flows out the bottom, keeps going until it comes to the sea."
"Good so far, Professor."
At some point unknown engineers put a dam here." Zavala drew a line across the top of the lake. "This blocks the water into the lake, but it's got to go somewhere or else it ends up sweeping around the gate." He drew a straight line away from the lake. "You cut this canal, and the water is diverted away from the lake to another riverbed." He looked up, triumph in his dark eyes. Now you can drain the lake."
"And build the temple. Here." Austin drew an X in the dirt with the tip of his boot.
Zavala picked up the narrative. After you lay the last stone of the pyramid, you close the canal sluice, open the lake gate. The lake refills in no time and hides the temple. Ergo . . ."
"Ergo, ipso facto, and voila! Only problem is, the sluice gate is made of moving parts. In time the gate deteriorates with no public works department to maintain it. What's left of the Mayan civilization is being crushed into dust by the Spaniards. That curve is a natural catch-all for anything floating down the river. Junk builds up in front of the lake gate like a dike, the canal sluice rots open, and the river is diverted away from the lake again. The lake is fed by a few streams, but eventually the water level drops, exposing the top of the temple. Which becomes overgrown with vegetation."
"So if we wait long enough," Zavala said, "the lake will eventually drop to where the temple is completely exposed again. Unless the water pressure from that reservoir busts through the old dam and raises the lake level."
Austin pondered Zavala's statement and nodded. "I'll tell you the rest of my theory on the way back."
As they walked through the forest Zavala got his revenge. "You've got to admit that's a damn nice piece of engineering."
It was Austin's turn to ignore the pun. "I agree. It allowed them to drain the lake again if they wanted to. That leaves open the possibility that they might want to reenter the temple. The entryway on top could be a blind. Like one of the false entrances they built into the Egyptian pyramids to fool grave robbers. I wouldn't be surprised if that's why they put the skeletons there, just for stage props."
"Some stage. Some props," Zavala said.
"Let's call in an air drop when we get back to the plane."
Minutes later, from the plane, Zavala radioed their wish list to the Nereus. He raised a quizzical eyebrow over one of the items Austin requested but asked no questions.