Million-Year Data Storage Disk Unveiled | MIT Technology Review.

This is impressive, although perhaps not too practical. They are using lines scribed on tungsten. The underlying data is expressed as QR codes (which will be forgotten in a few centuries at most, but that is a different problem.)

One problem is that they are using 100nm line width. While impressive, at that width it is invisible to optical devices (which have a limit of approximately 1 micron) without very complex optics and electronics. So they are going for high density, rather than long-term readability. On the other hand, it would be great for a 50 to 100 -year storage, which is longer than any existing technology can reliably handle.

http://arxiv.org/abs/1310.2961