The problem is that, despite the absurdly long, it is very narrow and, worse, it is made of local materials, which makes it the same color as the surrounding soil and rocks.

The traditional answer is "China's Great Wall", but this is not the case.

This is a photo of the Great Wall taken by the International Space Station with a telephoto lens:

In other words, to the naked eye, the Berlin Wall is completely invisible.

The problem is that although the Great Wall is ridiculously long, it is very narrow and, worse, it is made of local materials, which makes it the same color as the surrounding soil and rocks.

That is, there are many other artificial objects, yes, visible from the naked eye from space - especially if they are illuminated at night.

For example, this is a photo of the Egyptian pyramid taken from space orbit :

I like this photo, this photo was taken by an astronaut on International Space Station :

This is the first time that the launch pad of the International Space Station performs a manned mission. This photo was taken by Ivan Wagner two minutes before takeoff! You can see several details of the launch site in the center of the photo - as well as the adjacent platform - and some of the larger buildings at the bottom of the photo. The road is also easy to observe. The problem with photography is that you can't tell how powerful the lens is. A good telephoto lens can see details that cannot be seen by human eyes.

But you can calculate (very roughly) what we can see...

The International Space Station is about 400 kilometers above sea level. In good lighting conditions, the horizontal resolution of the human eye is 60,000 "pixels" (Warning: This number is very controversial and very similar, but we will use it. Our field of view is about sixty degrees.

So if we are going to see things on the ground clearly at a height of 400 km, this resolution on the ground is about 150 pixels per kilometer.

So, in theory, we will be able to see things in the size of thirty meters... This shows that the roads in the photos taken by astronaut Ivan are visible to the naked eye, and the photo itself is a good example we can see. .

We still have to consider the atmosphere "blurred" things - and seeing small objects requires excellent contrast - And "resolution of the human eye" is a very controversial issue.

But obviously you will be able to see large buildings without having too much trouble in orbit. That's what the astronaut said.