Both ends of the long building (pictured below) have five vents supporting massive fans to pull air through the structure. Behind it, there appears to be a water chilling system (visible below from the side) similar to the one built in Maiden. Pictured from the air (below, during final construction), Apple's initial building is just off the freeway but behind a hill, making the project site appear to be nothing but empty land to people driving past. The relatively small initial facility appears similar to a 21,000-square-foot secondary "tactical" structure revealed in permits at the Maiden site, as well as a 10,000-square-foot building Apple rapidly built in Oregon as soon as it acquired the land there.
The structure is reportedly surrounded by black lamp posts with cameras. Although only basic fencing is in place, security guards and two door access prevent authorized entry.
Now that the structure is finished, it's expected that Apple will take it online in the next few weeks, perhaps as a testing center to prepare for full deployment. In total, Apple owns 345 acres of land in the area which would allow for a massive facility.