The avenue ended at the edge of a huge, circular plaza four hundred paces wide.
Here, in the heart of Entry hall 300, the black dark rock stone floor gave way to massive nested rings of dark slate, each ring engraved with the sky-high charts of the pre-diluvian sky. Across the center of the plaza, rising out of the water like the ribs of an upturned ark, stood the Great Iron Arch.
Qiao Ming stopped twenty paces from the threshold, his lantern beam looking small and fragile against the huge expanse of metal.
The arch was eighty deep-water lengths wide from pier to pier, its single massive curve leaping sixty arm-lengths into the ceiling gloom before locking into the central keystone of the vault. It wasn’t built of stone. It had been forged from plates of solid star-fallen iron four inches thick, riveted together with iron pins the size of combat shields. Thousand years of exposure to the forty-hour salt water had turned the outer surface a dark, velvety black, with weeping streaks of pale orange rust marking the seams where the water had drained during last cycles.
This was the boundary.
Behind him lay the three hundred entry halls of the Outer Octant. The vast residential, office, and memorial halls where the citizens and sovereigns of the fallen world had taken refuge during the early stages of the flood. Ahead, sealed behind the massive iron valves of the archway, lay the Inner Depths: the forbidden chambers of the Golden…
