A fine nozzle and high-quality, well-calibrated extruder are absolute necessities for detailed prints like this. I used an E3D 0.25mm nozzle on my Prusa upgraded with the Bondtech-Mosquito extruder-hotend assembly upgrade (the single best Prusa upgrade I would recommend), and it turned out perfectly. The Bondtech extruder and the Mosquito hotend are very worthwhile upgrades by themselves. (affiliate links)
These coasters were designed from images of utility covers I took on the streets of Rome–they were all over the place, and I thought the individuality and thoughtfulness of each one and its design were really cool.
There are three different coaster designs here, and the file for each is named by the distinctive words on it. I've included a holder to keep them organized, but I also think it would be awesome to make one out of a nice piece of scrap wood. I added a layer of resin to my coasters to give them some more weight and durability (the imperfections you see in the pictures are from the polishing I did, not from the files themselves). Some of the details (mainly the lettering) are quite small, and I used a .25 mm nozzle to print this. Bigger sizes may result in some slicing errors, but you can always scale them up a bit if you don't have access to a fine nozzle. It's also pretty retraction-heavy, so make sure your retraction settings are dialed in before you print these.
Next time you're in a big city, take some time to notice the intentionality of its construction and the human effort that went into it. Or you could just print these!