Curved Tunnel ceilings are quite strong, as they distribute the pressure of the surrounding rock/soil quite well. So if it is covered with loads of rocks and soil it could probably hold another street passing over.
Another consideration is recognizeability and reproduction. When you want hundreds of banners, or maybe even put the image into thousands of metal armors, you don’t want a superrealistic picture.
Every liquid cooling system is pretty much that. Eventually you need to give it to the outside and the outside is usually air. Heck even river cooling for Power plants ends up “air cooling” through the rivers surface.