Cities under stone. Halls carved to a forgotten measure.

The null zones are not amorphous. At twenty-five-metre boundary precision the Southern Ural planforms resolve as nested geometry, not geology. The outer envelope is elliptical, eccentricities 0.15 to 0.42. Inside it, at 200-metre depth slices, the residual-wave amplitude draws standing-wave nodal figures — Chladni patterns for that cavity, that frequency, those boundary conditions. Sand on a brass plate accumulates at the nodes. The city occupies the same arithmetic in rock.

The compiler spent four years expecting irregularity and mapping symmetry. Natural cavities follow faults and lithology. These do not. Architecture as frozen vibration: the street plan is the solution to a wave equation. Depth changes the figure because depth changes the cavity. The halls of folklore were always a frequency.