For the original zone, see The Archives of Zoltun Kulle.
The Archives are a special area in Diablo III Adventure Mode, accessible only when there is a bounty associated with it, which can occur in any Act. They are reached through a portal that appears somewhere in that act. There are four possible events to appear in this zone:
The same set of events can also occur in Leoric's Gardens, Blighted Sewer, The Killing Grounds, Nephalem Proving Ground or The Bound Keep.
Visually, they are a large combat arena in The Archives of Zoltun Kulle. Its layout suggests that originally they might have been a PvP battleground.