craftgrrl | Anvil, or alternatives?

I'm hoping that there's someone out there who's worked with jewelry wire and metal that can answer this question... When flattening a piece of wire to harden it, the instructions often say to use a hammer and an anvil. While I have a hammer, I don't have an anvil, and I don't know if that type of thing is sold in hardware stores. I guess I'll check the next time I can, but has anyone used something else and had good results? I know it'll have to be something flat and hard enough to withstand hammering with metal, and won't break easily...

thanks!