Any photos tagged with a location are shown in Places on a map. The aim of this is to help you find photos more quickly.
If any of your photos are not shown in Places, this is in all probability because they haven't been assigned a location. This is often the case with photos taken on standard digital cameras. Smartphone photos are tagged with a location as standard, provided this hasn't been deactivated.
You have the option to change the capture location of photos. To do so, select the relevant photos and choose «Edit capture location» from the context menu. Now you can enter the location or mark it directly on the map. Please note: The capture location will only be corrected in myCloud, not in the image data. The EXIF data will not be overwritten.
The "Places" function is still in the "nova" phase.