Not sure exactly where I got this idea from, but several years ago I started collected rocks, soil, grass, or whatever from places Patrick and I had visited. Although we travelled quite a bit before living in France, we did add pretty significantly to the collection while being in Europe.
I need to still find some additional samples, but I think we're up to about 30 jars of places - like, Valley of the Kings in Luxor,
Yosemite National Park, Chateau LaFite Rothschild's vineyards in Bordeaux - you get the idea.
The only rule (which I broke only once) was that they had to be a place that we went to together. Turns out I have some grass from Stonehenge that I went to without Pooky.