The weathering patterns on the Great Pyramid's exposed limestone tell a story that most people never consider. An Italian engineer named Alberto Donini conducted an in-depth study of how limestone weathers over time, developing equations that relate rainfall duration to the degree of surface pitting. What he found challenges conventional timelines. The pitting visible on the pyramid's base blocks, once protected by casing stones, requires extended exposure to rainfall to develop. A few days or even weeks of heavy rain won't produce this effect. It takes sustained weathering over long periods. The evidence is physical, measurable, and raises straightforward questions about when these stones were first exposed to the elements. How long does it actually take for limestone to pit like this? And what does that mean for our understanding of the pyramid's age and the timeline of its construction phases?