The churches of the middle ages became very large. All that stone stacked up on itself meant special ways of building so that the churches did not collapse.
While the weight of stone ceilings and walls pushed outward and down on the church, huge stone braces called buttresses pushed back. The balance of pressure is what holds the church up. You can see the buttresses all around the outside walls of the church plan at the right.
The stone ceiling is held up not just by the buttresses on the outside of the church, but also by piers, heavy cylinders of stone, on the inside. It takes many piers arranged around the church to hold up the weight above.
The Christian culture of the times meant special ways to lay out the floorplan of a church. Medieval churches were shaped like a cross, bringing to mind the cross on which Jesus was crucified.
The head of the cross, containing the choir and ambulatory, is called the apse. It faces east, toward the rising sun. The ambulatory is a curved hallway that leads around the back of the choir. The apse usually has many chapels for private prayer radiating about its outside walls.
Leading west along the whole length of the church is the nave, the main aisle of the church. The nave could hold several thousand people for regular worship. It was not only very long, but very wide and very tall.
The transept is a large aisle running north and south across the nave, up by the choir. The transept is usually a twin to the nave, same size and looks. There are usually doors on the north and south sides of the transept.
The crossing is where the nave and the transept cross. This is just in front of the choir. It is where the priest stands to lead worship, and where the altar for the church stands. Some churches in the gothic age have what is called a crossing tower, or spire. This is a high, pointed tower right over the crossing, sometimes over 200 feet high at the top. Often you can see all the way to the top of the crossing tower from inside on the crossing floor.
The nave is the main aisle of the church, where most worshippers gather for prayer. Worship could get so crowded it was hard to move around. That's why most large churches had aisles. The aisles lead around the outside of the nave, transept and choir. The piers that help hold up the heavy stone vaults of the ceiling divide the aisles from the nave.
The floorplan is symbolic of the cross, but it's the walls of gothic churches that are the most noticeable thing about them.