"It is said that when Damascus-made swords were first encountered by Europeans during the Crusades, it garnered an almost mythical reputationa Damascus steel blade was said to be able to cut a piece of silk in half as it fell to the ground, as well as being able to chop through normal blades, or even rock, without losing its sharp edge." -Wikipedia
Personally I'd like to see this stuff in action!
That Wikipedia article is a little inaccurate...