What occurs when two barrel vaults intersect?

When two barrel vaults intersect, they create a groin vault. A barrel vault, which is essentially a series of arches placed back to back, extends in one direction and can cover a significant space. When a second barrel vault is introduced, crossing the first at right angles, the configuration leads to the formation of a groin vault.

This architectural feature takes advantage of the structural capabilities of both vaults, allowing for greater spans and more complex interior spaces. The interaction of the two barrel vaults effectively creates the distinct edges of the groin vault, where the curves from both vaults meet. This innovation was significant in the advancement of Roman architecture, enabling the construction of larger and more elaborate spaces in churches and other monumental buildings.