Ancient Waterway

Ancient Waterway is the main hall of the ancient aqueduct system found just past Dahlgur Oasis in Act II of Diablo III.

It is used to access the Western Channel, and eventually Waterlogged Passage (hidden behind the waterfalls, opened by two levers). After breaching the Western Channel, it can be used to access Eastern Channel as well.

In Adventure Mode, a Waypoint is found in the hall as of patch 2.2.0.

The door to the Ancient Waterway is locked and can only be opened by Zoltun Kulle. An attempt to unlock it without him will result in a message that it is sealed by a complex stone mechanism.

Inside, a projection of Hakan II appears.

Trivia
Eastern Flow Control and Western Flow Control are not separate zones, but are rather subzones of the Ancient Waterway. It can even be seen in the background.