What do you do with redundant code?

Question

I have a class, which is part of a code library project that was written for a particular purpose that is no longer required. So the question is what do you do with code like this? Do you simply delete it, or do you leave it in bearing in mind that future developers may come across it and not realise that they can disregard it or do you have some sort of archive system, is there a recognised "pattern" that is in use...