QR codes are the primary method I use for quick-linking GIS and cartography content, especially with public maps. I've used them in previous work, printing out these codes onto basic signage - like posters. But I believe they can be incorporated more fluidly into an environment.
Using what I've learned about 3D printing topographic renders, I've been creating "QR Blocks" - customizing QR codes into any 3D shape. Ones that can then fit into shelving, rest areas and other spaces. Placing these blocks into architecture lets them blend in with scenery, while simultaneously making them less susceptible to weather in outdoor areas than a poster or sign would be. 3D printing also reduces the cost of having to modify previously existing architecture - these blocks can be made to work with space that's already available.
I use Photoshop - or Blender - for this, and start out by customizing a QR code into whatever color scheme that the project I'm working with utilizes, to more easily visualize how it'll look in a 3D space. This also helps in finding a suitable location for separately designed vinyl adhesives of the code, to make sure it's still readable by mobile devices. The adhesive can be assembled on most convex and concave prints, without losing that readability. I'm able to create three dimensional QR codes to work with these blocks as well.