Final answer:
A series of arches placed back to back produces a vault, particularly the barrel vault, which is a continuous series of arches resembling a tunnel. Corbel arches created with layered materials forming a cantilever towards the center are another example of this building technique.
Step-by-step explanation:
When a series of arches are placed back to back, they produce a structural form known as a vault. The simplest type of vault is the barrel vault, which resembles a tunnel with a line of arches extending in a row. This architectural feature not only provides strong structural support but also creates visually appealing interior spaces. In history, such techniques have been employed in the construction of aqueducts like the Pont-du-Gard, as well as in the architecture of large structures like churches, where the modulated sizes of arches create a harmonious geometric logic.