Students study the various shapes engineers choose to make structures strong — in particular, triangles, arches, and domes. They begin by experiencing firsthand the forces of tension and compression. Then they construct a variety of forms, test their strength, and discuss how tension and compression are distributed by triangles, arches, and domes. The multimedia resources used throughout the lesson show many applications of these shapes used in ancient and modern cultures. Students also discuss examples of these shapes that they have seen in their own experiences.