Case in point: the Armadillo Vault, a self-supporting pavilion comprising 399 limestone slabs and spanning 52 feet, curving and bending around the columns of a 13th-century Venice building at this year's Architecture Biennale. No glue, no mortar, no hidden substructure to ensure the 24-ton edifice doesn't collapse—just really smart architecture.

At the heart of what architects and the engineers who work with them do is the opposition between compression (pushing together) and tension (pulling apart). The Eiffel Tower, the stone-clad cathedrals of Europe, every bridge ever—they all rely on balancing these two forces.

The Armadillo Vault goes a different direction. Because its limestone blocks form a series of conjoined arches—a classic form that turns compression into strength—it stands with only a minimalist system of tension ties that helps balance the structure at the ground level.