For this challenge, the most important elements I noted are: street numbers 54/56, a tram, a tram stop, a series of trees, and an estate agency of the "Nexity" brand.

Let’s focus on the tram first. By analyzing it, we can gather clues about the city it belongs to :

From the Google search results, it is highly probable that this tram is from Marseille, France.

Now that we have narrowed down the scope of the search, let's use overpass-turbo :

[out:json][timeout:25];

// Define the approximate bounding box for Marseille, France.
{{geocodeArea:Marseille}}->.searchArea;

node(area.searchArea)["addr:housenumber"="56"]->.location;

(
  // Find tram stops within 10m of the location
  node(around.location:10)["railway"="tram_stop"];

  // Find trees within 10m of the location
  node(around.location:10)["natural"="tree"];

  // Find Nexity agencies within 10m of the location
  node(around.location:10)["office"="estate_agent"]["name"~"Nexity",i] ;
)->.results;

.results out body;
>;
out skel qt;

Sorting through the results, we identify this specific location. In the bottom right corner, we can see a Nexity agency next to street numbers 54/56, along with the series of trees and the tram stop.

This leads us to the flag.