X-66 Hexcrete Archipelago

 is a location in the Big Empty in the Fallout: New Vegas add-on Old World Blues. It is directly north of the Z-38 Lightwave Dynamics Research station.

Layout
It is made up of many large hexagonal prisms sticking upright from the ground, varying in height from syscraper-esque, to as tall as the player character(maybe shorter than player too). There is also a pool of radioactive liquid with two metal boxes in it. Two packs of nightstalkers spawn to the south and east, in range to attack any player. Also, its proximity to the X-13 research facility means that any Robo-scorpions guarding it will attack you if you venture north from this location.

Appearances
This location appears only in the Fallout: New Vegas add-on Old World Blues.