It's three inches across, and it contains 15,000 pages of micro-etched human-readable linguistic information. The goal is to provide a Rosetta stone for the future. The disks are expected to last 2,000 to 10,000 years, and they're making a bunch of them and distributing them to various places to increase the chance that one of them will survive into the future.
When I say "human-readable," I mean "readable to anyone who can optically magnify the pages by 500 times." This is not digital storage; all you need to do is magnify it (and know one of the 2,500 languages represented) to be able to use it. There's a super-cool design on the front with languages spiraling down toward the center, getting smaller and smaller, to make clear that the idea is to use a magnifier.
And in addition to being an amazing idea, it's also gorgeous.
They're currently handcrafted, so a disk from the current prototype run would set you back $25,000. But I'm hoping that they'll make more of them that will be cheaper.
The Rosetta Project does other stuff, too. For example, they're "working to build a publicly accessible digital library of human languages." Sounds like a really worthwhile and interesting organization.