Félix Candela's Los Manantiales restaurant is a masterpiece of shell architecture, proving that concrete can be not only thick and heavy but as thin as paper and still strong. Its secret lies not in the amount of material but in the geometry of the form.

The building is composed of four hyperbolic-paraboloid (hypar) shells intersecting at a central point — like an eight-pointed, undulating flower or seashell. The hypar, though it looks curved, is a 'saddle' surface generated by the motion of straight lines; this double curvature distributes load along the surface as tension and compression and lets the shell support itself against bending. As a result the concrete is only about 4 centimetres thick even across a span exceeding 30 metres — the shell is, relative to its span, thinner than an eggshell. There are no columns and no beams; the shell itself is both roof and structure.

Candela was an architect-engineer who fled the Spanish Civil War and settled in Mexico; he earned the name 'shell master' (el cascarón) by making the mathematical hypar geometry buildable on site with cheap timber formwork. Los Manantiales is among the most elegant examples of a shell architecture in which form and structure fully coincide and the strength of the material comes not from mass but from geometry — a tradition running on to the Sydney Opera House and contemporary thin-shell structures.