So, we have a fair amount of one time improvements, such as the Endless Research Park and Endless World and the Trade Clearing Bureau. When they're built, not only will it announce to everyone in the game that someone built it, but it will cancel the contruction of it for any other faction trying to build it, and no other faction can build it. 


Basically, kind of a big deal. 


While the bonuses they provide are substantial, there is not much else to note about them besides the cool border their pictures get. For something so important, wouldn't it be cool if whatever you built became visible on one of the colonized planets in your system, similar to some anomalies like the Husk of Knowledge or The Platform of Ys. This is a minor visual thing, but I think it would add some cosmetic value to the systems where they are built and get a little crazy if you have more than one in the same system.


This could also be extended to one time empire wide improvements, such as the Academy Embassy. I just think it'd be cool to zoom in on your planets and visually see the unique improvements you've spent a lot of strategic resources and 10+ turns to build.