A barrel vault is best described as which of the following?

• A. A flat ceiling over a rectangular plan
• B. A dome resting on a drum
• C. A sequence of intersecting arches forming a groin shape
• D. A curved hallway formed by a continuous series of arches

Answer: (D)

A barrel vault is a long, curved ceiling formed by a single arch extended along the length of a space, creating a tunnel-like corridor. This matches the description of a curved hallway formed by a continuous series of arches, since the vault is essentially a continuous curve running along the space.

The other options describe different features: a flat ceiling over a rectangular plan is not vaulted; a dome resting on a drum is a dome, not a barrel vault; a groin vault comes from intersecting two barrel vaults, forming groins rather than a single continuous curved passage.