Complex sentence: To give an idea of scale, the Great pyramid of Giza of Egypt (the largest Eygptian pyramid) would almost exactly fit inside the cave chamber; that is, its base is approximately the area of the chamber floor, and its height is also similar.
Split into simpler sentences: To give an idea of scale: the Great pyramid of Giza in Egypt, the largest Eygptian pyramid, would almost exactly fit inside the cave chamber! Its base is approximately the area of the chamber floor, and its height is also similar.