The space was too vast for mortal sight to measure in a single glance.
Entry hall 545 was not merely a room within the Ark Nadir. It was the central stone-built tiered arena of the Fifth Tier, an arena two hundred arm-lengths across where the huge forces of weight, water, and stone came together into an eternal exact balance. Above the circular floor rose an unbroken hemispherical dome of dark hard speckled rock cut stone, spanning a hundred paces from springing line to crown without a single internal column to obstruct the view.
Around the outer edge of the tiered arena stood eight massive flying stone props. Each stone support prop was carved from a single course of grey mountain granite, twenty feet thick at the base, sweeping upward in a graceful, curved curve like the stone-hard ribs of a giant beast to meet at the apex of the dome.
At that apex hung the Eighty-Ton Keystone.
It was an eight-sided block of black dark rock eight arm-lengths across, seated into the center of the converging ribs without mortar, held suspended by sheer, unbending squeezing. On its downward-facing facet was engraved the Primordial Seal of the First Epoch—a stylized compass encircled by eight waves—beneath which hung forty-eight bronze sounding-bells that shook whenever the black tides shifted forty leagues above.
