#1 - Oct. 5, 2011, 1:54 a.m.
Blizzard Post
When the PTRs come back up, the Hour of Twilight dungeon will be available for testing on the PTR. This is actually the third of the three dungeons. Well of Eternity will become available soon.

The dungeon is still a work in progress, with VO, Quests, and early Dungeon Journal drafts in place.

There is also a known bug that will make the run back to the third encounter unintentionally long if you wipe. This should be fixed in a later PTR build.