What fruit segments inspired the shape of the roof shells?

The roof shells of the Sydney Opera House were inspired by orange segments.

The orange comparison describes the geometry used to solve the building’s most difficult design problem: how to construct the sweeping shell roofs. Jørn Utzon and his collaborators eventually based the shells on sections of a single sphere, allowing differently sized roof elements to share the same curvature.

The popular story is that Utzon discovered the idea while peeling an orange. Sydney Opera House’s own historical account treats that as an oversimplification: architect Eero Saarinen had used grapefruit and orange examples to explain thin-shell forms, while Utzon developed the spherical solution through models and geometric study.

This is also why “orange segments” is more precise than saying the roof was simply shaped like fruit. The fruit offered a visual analogy for arranging curved pieces; the finished roof is an engineered system of precast concrete ribs and panels, covered with ceramic tiles.