A noticeboard written in scent
You see plain pavement. Your dog finds a crowded noticeboard. Certain spots, often at a corner, a gate post, a lamp base or a gap in a wall, collect scent marks from dog after dog along the route, plus foxes, cats and food traces washed into the same cracks. Each visit layers new information over old: which animals passed, how recently, and clues carried in scent about their sex, health and mood. Sniffing for minutes is reading in depth, not dawdling, and his habit of finishing with a careful mark of his own is the equivalent of adding his reply to the thread for the next dog. The patch stays interesting precisely because the neighbourhood keeps updating it.
Why the weather never cancels the reading
Owners often expect rain to wash the attraction away, yet you notice he checks the patch just as thoroughly in wet weather. Rain does fade the oldest scent, but water also lifts and spreads scent molecules from porous stone and soil, making some notes easier for a dog to detect. Wind can push fresh scent from a nearby garden or bin store across the same spot. In dry heat, scent sits concentrated and close to the surface. In other words, each kind of weather edits the noticeboard rather than closing it. His consistency is also habit: a dog who has found rich information at a landmark once will always budget time to check whether anything changed there.
Giving him time without losing the whole walk
Sniffing is not wasted walk time. Allowing a dog to investigate scents lowers arousal, uses his brain in the way it was built to work and often leaves him more settled than an extra distance marched at heel. A practical compromise is to treat the famous patch as a planned stop: let him read it fully, then use a cheerful cue and a treat to move on, rather than dragging at the lead mid-sniff, which builds frustration at the same place daily. Vary the wider route for novelty while accepting this landmark will always be on his itinerary. If you are short of time, shorten the route, not his one great reading break. If you walk with another dog regularly, watch whether the two of them read the patch in turn or compete for it, since that tells you how valuable the spot is on their shared route.
When a favourite patch becomes an obsession
Ordinary devotion to a scent spot ebbs and flows with what has been left there. Pay closer attention if his behaviour at the patch changes sharply: if he becomes frantic, guards the spot from other dogs, refuses to leave for far longer than usual, or starts licking or eating material from the ground there, something on the surface may have changed, from spilled food to a substance you would not want him tasting. Move him on, check what he may have picked up and ask a vet if he is unwell afterwards. Note when the fixation intensified. For anything that still puzzles you about the change, put a follow-up question to KinsLe's Kimmy; she answers using the KinsLe Answers library.