It's easiest to use the editor to achieve this. The map literally needs to be completely filled with Launch Arcos.

There's a downloadable file if you want to see for yourself. IMO the concept is cooler than the execution. YMMV.

https://simcity.fandom.com/wiki/Arcology

Even if it's easiest done with SCURK, it's still achievable in the game itself. Just really difficult.

And yeah, the execution kinda sucks, but given the resource constraints at the time, it's understandable that it just exploded them all to fake launches instead of having an animated launch for each arco.

Ha! It’s been so long, I can’t remember if I ever hit that milestone. I had honesty completely forgotten about that aspect of it!