For a really special memory, you can mail home a physical object that says something about the location. Not in any packaging, but rather put the address and the stamps on the object itself. For example, when I was in Tonga I sent home a can of corned beef (one of their main food sources). Just wrote the address on top of the cylinder, then put the stamps all the way around on the sides. Also sent it registered mail. Be prepared to spend about 15 minutes convincing the post office staff that you really can send it through the mail.

Our mail carrier showed up one day with a bewildered look on his face and a bunch of forms to sign, saying everyone in the post office had been standing around trying to figure out what this thing was and where it came from. (This is a part of the country where most people have never owned a passport.)

I got the idea from someone who had on a shelf a large coconut which was sent through military mail about 30 years ago by his dad.