A thousand years ago you couldn't make bread until you had ground cereal grain into flour using heavy stones like these.

The grain was poured into a hole in the middle. The top stone was turned round over the bottom stone using a stick pushed into a hole on top as a handle.

Grinding the cereal grains between the stones turned them into flour which was then collected to make bread.

These two stones were found together in a pit and could still have done their job. It is a mystery why they have been left there for archaeologists to find.

You can see the stones at JORVIK in York.