Seems to me that if you want to build a large stone structure that will last a very , very long time,then a pyramid is a natural shape to choose. You can build a small one, and then make it bigger by adding a row of blocks to each level. Any other shape would probably be less stable or require more material or both. Before long, you would have enough knowledge about what building techniques work and what doesn't. If you are in Mexico, there is no need to be inspired by what the Egyptians did. You can figure it out the same way the Egyptians did: by trial and error.

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Rock is dead. Long live Paper and Scissors.