Past the Gallery of Pillars, the floor dropped sharply into a canyon within a canyon. An upright-walled trench carved thirty feet deep into the dark chert bedrock of the mountain.
Tomas stood at the brink of the descent, holding his lantern out over the void. The rock here was black, dense, and glassy, filled with nodules of dark flint that threw back sharp, needle-like reflections in the yellow light. For three miles, this underground river trench had served as the high-pressure chute of the River March, funneling the entire mountain watershed toward the constriction of the Great Siphon.
“Look at the width,” Nessa said. She knelt at the edge of the deep gap with her boxwood rod. “Sixteen feet across. The walls are almost perfectly upright, cut by high-speed gravel scour over ten thousand years. This channel was full. Then, the water speed through this throat was upwards of twenty-five feet per second. Nothing living could swim against that head. It was a high-pressure piston driving the whole lower river system.”
To go down into the trench, the Dragon-Slayer company had not relied on rope ladders. They had built a heavy-duty timber stairway.
Heavy eight-inch spruce balks had been notched into the chert walls, pinned with two-inch forged iron spikes, and fitted with heavy oak treads four feet wide. The wood was dry, gray with age, and caked with twenty years of limestone dust. But the massive joinery remained solid.
