# What is a basilica?
**A basilica is an architectural form in which a raised central nave is flanked by lower side aisles, separated by columns or piers.** The height difference creates clerestory windows in the upper walls of the nave, allowing daylight to flood the interior.
## Origin
The basilica form dates from Roman times, where the building served as a marketplace, law court, or assembly hall. After Christianity was legalised in the 4th century, the form was adopted for church buildings because it offered large spaces for congregations.
## Characteristics
– **Elongated floor plan** — rectangular with one or more aisles
– **Raised central nave** — higher than the side aisles, with windows in the upper walls
– **Rows of columns or piers** — separating the nave from the side aisles
– **Apse** — a semicircular recess at the far end, often with a half-dome
## Application
The basilica form is the most widely used plan in western church architecture — from early Christian churches in Rome to Gothic cathedrals. The basic principle of a high nave with lower side aisles remained the standard for centuries.
In modern architecture, the term is also applied to buildings with a similar cross-section, such as certain railway stations and market halls.
## Related terms
– Nave
– Column
– Vault
– Clerestory
– Apse
Want to learn more about construction terms? Visit our [knowledge base at fredsdiyplans.com](https://fredsdiyplans.com).