Many children are fascinated by the great pyramids of Cheops. These only surviving wonders of the ancient world were mathematical challenges to their creators, and they remain challenging today.
Children can decide how to make models of the pyramids.
A pile of dry sand or wet sand on a square base provides one example. Models in clay provide another. Students can experiment with different sizes of triangles to see what shapes of pyramids result. Other monuments of different shapes provide similar exercises in measurement and challenges for construction. Each structure provides distinctive features that lead to interesting mathematical questions, which the students themselves can formulate and explore.