How to add places to Photos?

Today I have serveral hours to travel. My Idea of fun should be to add places to my old pictures i Photos.
I was a bit surprised to see that I couldn´t do that.
Or can I? How?
(And no, I don´t have my mac with me for this trip)

You could use a geotag app like Geotag Photos pro or MaPic. (I’ve used MaPic myself in the past)

The location (and altitude) are exposed to AppleScript, so you could do this with Automator or Keyboard Maestro. Of course you would need the lat/lon of each location.