A Spanish builder, [Rafael] Guastavino (1842–1908) emigrated from Barcelona to New York in 1881. He was experienced in designing and constructing traditional Mediterranean-style thin ceramic tile vaulting—self-supporting arches and vaults built from layers of interlocking terracotta tiles bonded by mortar. It’s an old technique that can be traced back through medieval Gothic cathedrals and ancient Roman temples. Guastavino made its affordability, light weight, strength, and—especially—resistance to fire modern selling points.
Interesting article – with good pictures! One of them is a construction view, showing how thin the tile vaults really are – with Guastavino supervising.