A barrel vault, also known as a tunnel vault, wagon vault or wagonhead vault, is an architectural element formed by the extrusion of a single curve (or pair of curves, in the case of a pointed barrel vault) along a given distance. The curves are typically circular in shape, lending a semi-cylindrical appearance to the total design. The barrel vault is the simplest form of a vault: effectively a series of arches placed side by side (i.e., one after another). It is a form of barrel roof.

As with all arch-based constructions, there is an outward thrust generated against the walls underneath a barrel vault. There are several mechanisms for absorbing this thrust. One is to make the walls exceedingly thick and strong – this is a primitive and sometimes unacceptable method. A more elegant method is to build two or more vaults parallel to each other; the forces of their outward thrusts will thus negate each other. This method was most often used in construction of churches, where several vaulted naves ran parallel down the length of the building.

Barrel vaults were first used in ancient Roman architecture, and they were later adopted by Byzantine and Gothic architects. They are a common feature of many types of buildings, including churches, mosques, and synagogues.

Here are some examples of buildings with barrel vaults:

* The Pantheon in Rome

[Image of Pantheon in Rome]

* The Hagia Sophia in Istanbul

[Image of Hagia Sophia in Istanbul]

* The Notre Dame Cathedral in Paris

[Image of Notre Dame Cathedral in Paris]

* The Sagrada Familia in Barcelona

[Image of Sagrada Familia in Barcelona]

* The Taj Mahal in Agra

[Image of Taj Mahal in Agra]

Barrel vaults are a beautiful and versatile architectural element. They can be used to create a variety of effects, from a sense of grandeur to a sense of intimacy. They are a reminder of the rich history of architecture and the ingenuity of builders throughout the ages.