Square are found everywhere from buildings to parks to grids for planning. Due to the congruent sides of a square it is not always the most practical rectangular shape to use. In fact, often times when a square and a rectangle have equal perimeter, the rectangle is used more often because the wall space is more useful. Octagons, the first truncation of the square, are not used much in architecture anymore. Orthodox churches are historically known for their octagonal shape.
Rectangles play the most important role in architecture.
Rectangles are the shape that is seen most. They are used everywhere from buildings, streets, doors, and many more. Rectangular projects are often times the most comfortable, useful, and easily built. Because the rectangle is based on the right angle, its geometry is elementary. Size is determined by need, material limitations, site limitations, and budget.