The church groundplan consists of the following fundamental elements:

The nave:

Narthex – A low projection at the western end of a church, like a porch.

Nave – The main body of the church, the central approach to the high altar.

Side Aisles – Open area of a church parallel to the nave and separated from it by columns or piers.

Transepts:

Transept – An area set crosswise to the nave in a cruciform (“cross-shaped”) building

Chancel – The space around the altar in the sanctuary at the liturgical east end of a traditional Christian church building. It may terminate in an apse.

Apse:

Choir – The area of the church between a transept and main apse. It is the area where the service is sung and clergy may stand, and the main or high altar is located.

Ambulatory – A semicircular or polygonal aisle. Often an ambulatory leads around the east end of the choir; separating the choir from apses or chapels.

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The choir: the liturgical heart of the church

The choir is an essential part of religious architecture. It is the space dedicated to liturgical celebrations, where clerics gather to sing and pray. Its position varies according to architectural style and era, but it is generally located at the end opposite the church's main entrance.

As you can see from this diagram, the chancel is often located in the apse, the semicircular or polygonal section at the end of the church. The main altar is usually located in the center of the apse.

Why is the choir placed here?

• Focus: The shape and position of the apse are natural eye-catchers. The choir, by being located here, becomes the center of attention and underlines the importance of liturgical celebrations.
• Symbolism: The apse is often associated with the East, symbolizing light and God. The choir, placed in this part of the church, thus recalls the direction towards which the faithful turn during prayer.
• Acoustics: The rounded shape of the apse ensures good sound diffusion, which is particularly important for sacred music.

Different types of choir:

• Ambulatory choir: In some churches, the choir is surrounded by an ambulatory, a passageway that leads around the apse. This allows the faithful to circulate around the choir and admire the decorations.
• Choir without ambulatory: In other churches, the choir is directly accessible from the nave, with no intermediate passage.