Begun in al-Andalus under the Umayyad emir Abd al-Rahman I, the Great Mosque of Córdoba shows how a hypostyle (many-columned) hall can be made airy and tall through a structural invention.

The builders had many columns reused from earlier Roman and Visigothic buildings; but these columns were short and could not, on their own, carry a ceiling at sufficient height. The solution was ingenious: a pier was set on top of each column and two tiers of arches were raised. The lower horseshoe arches tie the columns together; a second tier of arches above, springing from the tops of the piers, carries the ceiling. In this way a tall interior was obtained from short columns through a two-tier arch system.

The voussoirs of the arches were built in alternating red brick and white stone; this alternating colour scheme is both structural (a stacking of different materials) and visual — a rhythmic line that carries the eye along the arch. Hundreds of columns and stacked arches turn the space into a "forest of columns" with indistinct edges and a sense of the infinite. The Mosque of Córdoba is thus an example of structural intelligence that turns a material constraint (short reused columns) into a design opportunity.