Dropping past the service galleries beneath the Iron Cenotaph, the heat dropped once more, replaced by the heavy, clinging humidity of stale oil-drain pits. Here in Entry hall 664, the stonework widened into a tiered arena of giant stone iron cylinders. These were the main water-pressure accumulators of the lower castle walls. Huge cylinders cast from star-fallen iron, fifty arm-lengths in width, rising out of a dark lake of stone petroleum.
Qiao Ming walked along a raised iron narrow high walkway that curved along the outer edge of the metal tube wall. His bare calloused feet felt the slick, thick, sticky glaze of condensed oil-film that coated the punched holes in plates. The narrow high walkway had no handrail. It was merely a shelf of cast iron three spans wide, cantilevered over a drop that vanished into total blackness. He moved with slow, balanced deliberation, his prehensile toes gripping the corrugated diamond tread.
Behind him, Yan Zhiqiu carried the horn lantern low to light up the path. The amber light reflected across the surface of the petroleum below. That turned the liquid into a vast, rainbow-bright mirror that shone with shades of peacock-green and bruised purple. Suspended directly above each metal tube was a piston of solid star-fallen iron, suspended from braided steel cables thicker than ancient cedar trunks.
