styrofoam
well done
Some of the monuments in Washington DC, National Mall should last through the ages. Lincoln Memorial, Vietnam Veterans memorial, maybe even The Washington Monument. (unless an earthquake topples it)
They would be severely degraded after 2000 years but something would be there.
Did you mean the US instead of North America? Because there are real, actual pyramids in Mexico.
I don’t know about Mt Rushmore, although that’s not a bad choice. I’d say city skyscrapers are a better candidate.
If Apollo landings are still the answer 4000 years from now, that will really really suck.
global Warming.
Washington is a low-lying Coastal city.
Many will be partially submerged, until the foundations fail.
I came in to nominate pit mines and see that the_diego already did.
They’re going to wonder what the hell happened to cause us to farm in that fashion.
The lunar artifacts are a good call too. Solid proof of Ancient Aliens® helping us excavate those terraced pit farms. (or are declared a hoax)
I doubt skyscrapers will last . In a thousand years, they will probably be piles of rubble. They aren’t really designed to last centuries (or even decades) without maintenance.
In fact, many of the Egyptian pyramids that more cleverly designed (read: more cheaply and easier to build) are now featureless piles of rubble - they were made with cores of cheap mud brick and rubble during the Middle Kingdom - that’s why the Old Kingdom pyramids (made expensively of solid rock) are iconic - they lasted. The Middle Kingdom pyramids all failed once the outer casing of stone was ‘scavanged’ or eroded.
Modern buildings are made very cleverly (and cheaply, for what they are). Once the windows are out and rain starts to work its way into the structure, I doubt they would last long - a century or two at most. Some parts would corrode, and that would be the end of them. Hell, the building I work in had its facing of stone start to erode (and fall into the street), and it is maintained - and was only build in the mid-seventies.
Perhaps the best place to get an idea of what a modern city would look like after abandonment is the containment zone around Chernobyl - after 25 years, most of the buildings are still standing, but in a dangerously fragile state, many with collapsed parts and trees growing out of 'em. I doubt any will last past 100 years, but then, they were build crappy Soviet-style. Western ones ought to last longer, but not by a huge factor.