You’ll find the best secrets in places that would actually be used by people. Look for a rusted rail switch that still moves, a loose track guard that hides a crawl‑space, or a damaged signal box that opens into a maintenance tunnel. Old stations had spare rooms for crew, so a cracked concrete pillar or a broken service door can be a good cue. Keep the clues subtle—just a few shifted tiles or a rusted bolt that turns—so the player feels like they’re uncovering something that was meant to be hidden, not just a game trick.