Question

According to the author, a ________ is actually an arch extended in depth, as if there are “many arches placed flush one behind the other.”

Answer 1

The answer is barrel vault, it is also known as tunnel vaults. It is commonly found in the ancient building like the churches, museums and government buildings.  One of the most important parts of the vault is the arch. The arch can support a huge amount of weight this is why it has been used by the builder since.