Poland's changing borders over the last thousand years

We have discussed here before how borders change.

I came across http://polmap.republika.pl/polska1.htm which I thought might be of general interest.

It shows how Poland's borders have changed over the centuries. The text is in Polish, but you don't need any Polish language skills to work out what the "next" and "back" buttons do, and that clicking on a century or date at the bottom of the screen takes you to a map of Poland as at that time.