Going back to the USB drive discussion a month ago, I still have a 1GB Memorex thumb drive. It survived about five or six trips through the washer and dryer and it occasionally still works. It’s the only one I ever found with a lock switch so you could make it read-only.
The TV show Babylon 5 had “data crystals” as a portable and durable data storage device which were rated for 50GB. Researchers at the UK’s Southampton University just blew that out of the water. From the picture in this article, the disc looks to be about 1.5" in diameter, or just a little larger than a US 50 cent piece. 360TB storage, rated for 14 million years and up to 350 degrees Fahrenheit.
I don’t know if that material can be made be re-writable, but it’s pretty impressive as an archive medium.