The difference between the two is that a vault is an arch that has been extruded into the third dimension, whereas a dome is an arch that spins around its vertical axis. Thus, they can be thought of as two-dimensional or three-dimensional versions of the same structure. There are many ways to describe the shape of a dome. It can be said to have a spherical appearance because it has the same radius at all points on the surface. Or, if we look at it from the side, it will appear to be an elongated sphere with one end thicker than the other. This is called elliptical symmetry. Or, finally, it can be described as a shell structure with alternating thick and thin sections connected by columns. Domes are used in architecture to create a spacious feeling inside a building. They are often used as religious buildings or for government institutions, but there are commercial structures such as shopping malls that use domes too. The main advantage of using a dome shape is that it allows more light inside the building than a structure with only walls would. A dome also provides cover for outdoor areas like courtyards or parking lots. Finally, it should be noted that a dome can be either internal or external.