Entry hall 618 was dominated by a single load-bearing marvel: the Resonant Pillar of the Southern Arch.
It was a huge hollow world-cedar forty paces in width, rising from the floor of the terrace and soaring eighty yards into the ceiling vault. Unlike the solid trunks they had crossed earlier, this ancient giant had been hollowed out by the pre-flood water-scribes before turning to stone, transforming its inside bore into a huge tone check-chimney pipe that connected the upper forest canopy directly to the underground water beds fifteen thousand deep-water lengths below.
The outer walls of the pillar were eight arm-lengths thick, composed of dense, dark heartwood that had stone-hardened into a ringing timber as hard as bell-bronze. Carved around the outer rim of the trunk were twelve spiral stairways and three hundred tone check-ports. It was narrow, upright sky-slits that allowed the internal air currents to escape in controlled, musical flutes.
As Qiao Ming and Yan Zhiqiu approached the base of the pillar, the air began to vibrate with a deep, sub-bass drone that made the fabric of their tunics flutter against their skin. It was a deepest tone of fifty-five hertz—a low, physical hum that bypassed the ears entirely, shaking directly in the pelvic bones, the ribs, and the marrow of the spine.
