It's possible the image you uploaded contains geographic coordinates.
EDIT: this is exactly what happened with my image upload, for example
EDIT: this is exactly what happened with my image upload, for example
My mind was blown when I saw rainbolt uncrop a picture.
Anyways as mentioned elsewhere: when I tried it the vision api was overloaded but I still received the location data. And it was from a picture taken inside my car (no landmarks or horizons visible).
I've tried with personal photos and was able to get very accurate guesses just with flora and architecture in the background of a photo.