PvP with heroes, Nightfall feature?

I had thought from the discriptions of Nightfall that there would be arenas that one entered with ones heroes, and did what was effectivly a 1v1, but with heroes on both sides too.

I have yet to find this arena. Is it something that is only accessable to pve characters playing though nightfall?

If it is accessable with PvP characters, I would very much like to know how and where. http://www.theamazonbasin.com/gw/forums/index.php?showtopic=6925