3 ideas
Treat the physical city as an active source of evidence rather than a backdrop. Routes, distances, which neighbourhood a person would plausibly be in, and what can be seen from a given street corner all constrain who could have done what, and when. Reading the plot then means reading the map, so real topography, not authorial fiat, eliminates suspects and exposes lies.
A photographer is trained to frame, fix a moment, and notice details that others' eyes slide past, such as light, position, and what sits at the edge of the frame. Applied to a crime, this professional habit becomes a detection method.
Grounding a puzzle mystery in verifiable real streets and districts makes the game with the reader fairer and more gripping. The reader can in principle check the clues against a map they know, so the solution feels earned rather than conjured. Local specificity replaces the sealed country house of classic puzzle fiction as the closed system within which every clue must hold.