Not a scientific achievement, but doesn't the Sagrada Família count?

"On 19 March 1882, construction of the Sagrada Família began ... It was anticipated that the building would be completed by 2026, the centenary of Gaudí's death, but this has now been delayed due to the COVID-19 pandemic."

Continuing construction (admittedly not continuosly) for roughly 150 years is pretty impressive in my opinion.

https://en.wikipedia.org/wiki/Sagrada_Fam%C3%ADlia

The Netherlands would like a word. Holding back the sea was a monumental project that will definitely last generations to come. Maybe not as exiting as high temp superconductors and fusion but still a nationwide unique product.

It may last for generations to come, but did the original development take generations?

Old-school land reclamation worked by putting woven fences in the water where waves would deposit sand over decades and centuries, slowly growing the land bit by bit. Those versions were already multi-generational projects.

(I'm citing the techniques used in the north frisian wadden sea, I'm unsure if the same techniques were used in west frisia as well)

Oh, that's very interesting. So I'm guessing that technique was used to make areas that were put of the water during low tide, and then eventually dikes were added to make them dry land?

Exactly. But this technique only allows you to get land that's exactly at sea level, so dikes are absolutely necessary.

This also means you need drainage systems to remove the water from already reclaimed land, as it's still exactly at sea level and will be relatively wet marshland otherwise.

Thats why the netherlands built those old school windmills. thats how land was reclaimed below sea level. They no longer serve the same function but are used instead for small shops and for tourists.

Many churches built before the industrial age took multiple generations to build.

Modern civilisation may not have multiple generations left.

And it might not even take an all out nuclear war, social media may turn out to have been even more destructive than nukes.

Also in the era of family businesses, businesses were much more sustainable, sometimes competitive over hundreds of years. The useful lifespan of a modern public company is much smaller.

Decommissioning a fission power plant and storing nuclear waste in a safe way? That's probably a multi civilization project. The easy part first.