The first part of this gallery highlights photos whose location is elusive (but not impossible to work out) while the second part shows the latest pictures where someone has set or altered the location on the map; this second part is generated automatically.
Marking locations on the map is open to everyone who enjoys doing it, as is correcting the position of a previously marked location.
When you look at a photo, if it has been placed on the map you will see a button "Show Location on Maps" which you can use to look at the location on a variety of maps. If you choose Google Maps or Bing Maps you will also see an option to correct the position.
If it has not been placed then the button will say "Mark Location on Map" and you can then use it to place the photo. You can choose between Google Maps (either map, satellite view or streetview) and Bing Maps and more instructions will then appear.
If you do mark a location on the map, there is no need to post a message saying it has been done unless there is a question or you think the location in the caption needs to be changed.
You can also see the photos that have already been placed on the map here.