I can’t think of a single thing built in the last century that will still be there in a thousand years. We may still build some cool stuff, but none of it is durable anymore it seems.
Survivorship bias. The ancient stuff that survived to the modern day are not more durable than contemporary engineering, they’re just the 0.1% of structures that managed to survive this long.
The problem isn’t that we can’t build something that will last a millennium, it’s that we rarely, if ever, need things to last that long. Nuclear waste storage facilities are the only thing that comes to mind. Everything else would need to be torn down and renovated or brought up to code at some point.
The ancient stuff that survived to the modern day are not more durable than contemporary engineering
Basically any stone structure made for any reason will vastly outlast any steel reinforced concrete structure. Although concrete might appear superficially stone-like and unchanging it is actually porous and chemically active. Within about 100 years the steel rebar inside a concrete structure will rust, expand, and crack the concrete apart. Freeze-thaw cycles and plant activity will reduce it to rubble shortly thereafter.
Meanwhile a piece of stone block was already about a billion years old before it was cut out of the ground. A stone structure might be destroyed by earthquakes or human activity, but it does not have a built-in self destruct sequence countdown timer like SRC does.
The problem isn’t that we can’t build something that will last a millennium, it’s that we rarely, if ever, need things to last that long.
We absolutely can and sometimes we do.
Hitler’s flak towers are not going anywhere. There’s other 20th century buildings which can last a thousand years with occasional maintenance, but those flak towers, nothing will take them down.
Most very old buildings that survived to this age, survived because the locals had a use for them and maintained them, or because they had a pyramidical shape. The colloseum was a castle, the parthenon a church, … Without that usage, we’d only have the foundations and a few basements left.