I collect Dirts of the World.
A long time ago, I started asking anybody who was going anywhere to bring me back some dirt. Most people just put a little bit into the film cans people used back then, but sometimes they will put it in a little decorative box or container from the country, so I get a bonus present!
And a couple went above and beyond - my collection includes a little chip of the Coliseum in Rome, the Great Wall of China, and a bit of dirt from Jim Morrison's grave. (Yes, if everybody did that, it would be just awful, and nobody should ever do it, and I never asked for anything but dirt from the country so don't hate. All countries have plenty of dirt.)
In recent years, of course, the dirt has to be sort of smuggled, so what people will usually do is - hmm. I still have some countries left to go, so maybe it will be better if I do not go into strategies.
Visitors from here and there are always tickled to see a little bottle with their country's dirt, and when I plant something that originated in a particular country, I can put a tiny, tiny pinch of dirt from there in to help it grow and give it good luck!
But the best part is to always have so much of the whole world right here with me, and I like to think that all the dirts are as excited as I am when a new one arrives.
It will probably take my whole life, but I hope that by the I am old, I will have dirt from every country - the world on a shelf!