I watched a show that asked this question. The undisputed champ was Hoover damn Mt. Rushmore with an estimated expected life of hundreds of thousands of years.

EDIT: It was Mt Rushmore not Hoover Dam.

Hoover and three gorges dams. That much cement will be noticable for a long time.

“Low cost” levys and break waters, since those just use large cut rock dumped in the water.

A lot of modern engineering uses a more advanced type of cement than the ones ancient people used.
It’s chemically stable so it doesn’t react with the environment and has a predictable lifespan.
A side effect of this is that it predictably only reliably lasts about 100 years.
Older cement could react with the environment, which meant sometimes it broke really fast, but also sometimes it is able to heal small cracks and last indefinitely, if it doesn’t get a mold outbreak.

The pyramids are basically a big pile of rocks, so that isn’t going anywhere.

So for modern buildings, you’ll want to look for structures made from cement intended to last a very long time with low maintenance near water, like the biggest dams, or things made out of cut rock, like low cost commercial port break waters.

We just don’t make as many structures out of raw rock or crappy cement anymore, so it’s not as likely for a lot of buildings to survive.
On the flip side, we do have a lot more buildings, so they’ll probably find random elementary schools in Nevada in 4k years.

A process, instead of a thing:

political-election based rule, selecting for narcissism/machiavellianism/sociopathy-psychopathy’s rule.

IF humankind survives this-century’s The Great Filter, in-which Kahneman System-1 ( “Thinking Fast & Slow”, the most-important psychology book in the world, now ) fights to break System-2/considered-reasoning from having any authority,

and is winning.

ALL the ideology/prejudice highjackings-of-countries happening everywhere throughout our world, these days, are just “makeup” on the underlying animal-reaction-mechanism fighting-off considered-reasoning from this world.

So, in order to survive, humankind requires to break System-1 from authority, globally.

ALL ideology/prejudice addiction-styles, left, right, religious, anti-theist, ALL of them, have to be broken from rule, XOR humankind force-extinguishes itself, this-century.

It’s incredibly elegant, actually:

I believe that all worlds who cross the threshold heading toward their own Industrial Revolution sequence ( so I’m talking about the Roman Empire’s crossing of the threshold ), can have the same ScientificallyTestablePredictions/“prophecies” dropped into them,

about how there will be #ClimatePunctuation and #SpeciesWideCivilWar & #GlobalFoodWebCollapse … and all-3 of these predictions are in the Christian Bible’s Revelations-book, you can drop these same predictions into ALL worlds going into their remaining-toddler-unconscious-mind while having planet-crushing-industry & planet-destroying-military … and the result will consistently be the same: toddlers aren’t responsible, and TANTRUM/POGROM instead of growing-up.

Which is exactly what humankind’s going to be doing for about 6 decades, once things blow-up, in about 1 decade.

I don’t expect much in the way of survival of humankind, at the end of this century.

If any.

However, Universe/consequences/karma, whatever one wants to label the force-of-nature, isn’t going to cater-to our toddler-mind’s god-complex, and Universe is going to corner us into force-enduring consequences until either we’re extinguished, xor our remnant is grown-up in nature, no-longer toddler-nature.

All the 600+ mass-shootings in the US last-year, were narcissism’s lashing-out & tantruming/pogroming others, to “get even” with not being catered-to.

Our entire-species is in the process of setting-up that, at planet-scale.

Russia & Israel are committing “mass shooting” against other nations, for their genocidal narcissism…

US Civil War Part2’s going to be an internal demonstration of it, within 1 decade.

Everywhere.

All at once.

Our species’s epitaph.

Tantrum/pogrom was the best we could do: growing-up was “too hard” and unendurable.

That’s what we’re carving in Universe’s eye, now.

Its basis is wrong-sorting, preferring narcissism/machiavellianism/sociopathy-psychopathy for authority, suppressing responsibility & hard-lessons-learned from authority.

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