Need to find all the photos you took in France? You can use the Map Searches sidebar to do just that, provided your photos have been geotagged.
Expand the Map Searches sidebar, press and hold the Ctrl key and select the desired region on the map using the mouse. You should then see markers on the map. Each marker displays the number of found photos in the specific location, and you can use the mouse or zoom buttons to zoom in on the map to see thumbnails of the found photos. You can also see all found photos in the main pane. If you press and hold the Shift key and then click on a marker on the map, digiKam will highlight all the photos belonging to this group in the main pane.
digiKam also allows you to save map searches. This way, you don’t have to perform the same map search every time you need to find photos in a specific region. Enter a name for your search in the field below the map and hit the Save button. This adds the search to the My Map Searches section, and you can activate the saved search at any time by clicking on it.
By the way, digiKam supports both Marble and OpenStreetMap maps, so you can use the map you like for viewing the found photos in the Map Searches sidebar. You can switch between the Marble and OpenStreetMap maps using the Map Settings button.
Thanks to Gilles Caulier for the tip.