As in comparative anatomy it is easy, from a single bone, to designate and describe the animal to which it belonged, so in architecture it is easy to restore, by a few fragments, any ancient building. In consequence of the known simplicity and regularity of most antique edifices, the task of restoration, by means of drawings and models, is much less difficult than might be supposed. The ground work, or some sufficient parts of it, commonly extant, shows the length and breadth of the building, with the positions of the walls, doors and columns.