The Hive Outpost is located west of Liberty Bay, here. It is one of the Mini World Changes (Hive Outpost Mini World Change), meaning it won't always be there, only when the MWC is active.
You enter the outpost using a ramp to the ground floor. Once there, you can go up or down to find stronger creatures on the top-most and bottom-most floors.
Spoiler warning: Quest and/or game spoiling details follow. (Settings
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The Hive Outpost is one of the spots you have to cartograph during the Cartography 101 Quest
Spoiler ends here.