Yes, the Pantheon is a good example of what I was talking about — except that it&#x27;s built with Roman concrete, which is substantially more weather-resistant than modern concrete, for reasons that are still not well understood.  It&#x27;s probably a matter of using slightly different pozzolans, but the Roman concrete manufacturing process was lost with the fall of the Western Roman Empire.  So if you were to try to build a Pantheon today, you&#x27;d have a good chance it would fall down in only a century or two.<p>Lime cement, though, we do still know how to make, and it has the advantage of having a lower TCE, which will reduce thermal-cycling stresses on your wall when combined with other low-TCE materials like granite.<p>Both lime cement and Portland cement can suffer pretty badly from acid rain, a problem that was only discovered in 1853 (just yesterday, in the lifespan of the aqueducts or the Pantheon), and which I think we&#x27;re well on our way to solving.  It might come back, though, and it&#x27;s harsher on lime cement than on Portland cement.<p>This should reinforce my point above about surprising failure modes in things that you think you&#x27;ve &quot;overengineered&quot; to last for the ages.