Designed in Spain by Frank Gehry, the Guggenheim Museum Bilbao marks the threshold where architectural form passed from paper and model into the digital model. Gehry's curving, twisting forms, conforming to no traditional geometry, had until then been considered impossible to draw and to build.

The solution came from outside architecture: Gehry's office adapted to architecture a three-dimensional modelling software called CATIA, used by the aerospace and automotive industries. Gehry first found the free forms by hand in paper and physical models; these models were then digitally scanned and turned into a precise numerical model in CATIA. This model calculated the exact geometry of every curved steel structural piece and every titanium cladding panel for fabrication and assembly. The seemingly arbitrary form thus became numerically definable and therefore producible — every panel unique yet fully defined.

The outer skin is clad in thin titanium sheets, forming a softly curving surface that changes colour with the light and weather. The building also turned a declining industrial city into a centre of culture and tourism, launching the urban transformation known as the "Bilbao effect." But the architectural lesson is structural: the Guggenheim Bilbao is the building in which digital design made free form buildable and opened the age of parametric architecture.