North pillar

One of four legs, isolated. Zoom in with the wheel: each post is a box of four chords laced with flat bars, braced in X-panels between horizontal belts.

Why this shape? Wind & form

Wind pressure grows with height, and the wind force acts on the tower's whole silhouette, so the overturning moment is largest at the foundations. The legs spread to 125 m where that moment is greatest, giving the leeward legs a long lever arm.

• Widening base. The moment from the wind above any level grows rapidly toward the ground; the width 2X(h) is the lever arm that carries it. Over the lower ~110 m the resulting leg force stays within about ±10% of constant.
• Curved profile. The outer edges follow an exponential-like curve, so wind and weight stay inside the legs and members mostly carry axial tension and compression rather than bending.
• Open lattice. Gaps let the wind through: the lattice presents a fraction of the silhouette area, and the narrow upper shaft catches little wind.