Like the modern road network? The rail network? The world wide electricity grid? The internet?

that's moving the goalposts as to what constitutes took X years to "complete". you can use any of those things after a few years of construction. But they are boundless for expansion.

I have a hard time grasping what this thing could even be. Technology seemingly moves much faster now than it did back then. Anything we start now, in 200 years could look like it was started in the stone age. But again, i cant even imagine what that something is.

After millenia of using horse powered travel we've gone from vehicles, to planes, to the moon, to mars in about 100 years.

The Liverpool and Manchester Railway (steam powered trains): 1830.

Daimler (internal combustion cars): 1892.

Wright Flyer III (plane): 1903

Apollo 11: 1969.

Even steam powered trains were almost inconceivable to the average person living in say, 1700, just imagine what that person would have thought about Apollo 11! Heck, I imagine even Napoleon in 1821 couldn't really imagine the mechanized world awaiting just 50 years in the future.

Imagine how big of a stone structure we could build if we used modern CAD and CNC and just stacked giant bricks for 200 years. We should be one upping the pyramids and churches.

* high-speed rail with similar scale to the US interstate system.

* subway system in Los Angeles on par with NYC

* any-speed rail link between US and Russia

* (saw this from a poster below: interstellar probe )

Maybe a new fighter jet

Practically though, this doesn’t really make sense. Kind of like waterfall development but tripled down on all the bad parts