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The incomplete Occupy HQ. (Lydia DePillis)

As the cold descends, McPherson Square’s occupiers have kept busy figuring out how to keep themselves comfortable. A key part of that planning came together last night, in the form of a one-room building that’s been called a shed, a barn, and most often simply a “structure,”  for the purpose of holding general assemblies and serving as an emergency shelter.

That was one infraction too many for the Park Police, who have been arresting people and surrounding the square with vehicles all day; occupiers on the roof have donned gas masks in anticipation of being pepper sprayed. At the time of this posting, most of those gathered in the incomplete frame have been carted away.

I’m more interested in the building itself, though. It’s an elegant design, with walls that lean out to create a very roomy-feeling interior. According to one of the architects, Cecelia Azurduy, the shape is symbolic, rather than structural: It’s called the “People’s Pentagon,” mimicking the headquarters of the U.S. military. “We wanted to reclaim the geometry,” she says (here’s a better view of the shape).

The shell of the building, made out of two-by-fours and plywood, was constructed within the span of a few hours last night. It went quickly, because whole thing had come in six prefabricated pieces, and only needed to be bolted together with a drill. The plan, according to Azerduy, had been to roof it with tar paper and face the south wall with plastic sheeting for light and passive heating. The builders also planned to strap water bottles to the walls as insulation, filling them halfway with water to better serve as a heat sink. The floor was to be covered with hay, and the walls have stepped benches for stadium seating.

Throughout the afternoon standoff, occupiers have insisted that the structure is legal because it’s “temporary,” and not rooted to the ground. That’s sort of true. The relevant Park Service regs read:

In connection with permitted demonstrations or special events, temporary structures may be erected for the purpose of symbolizing a message or meeting logistical needs such as first aid facilities, lost children areas or the provision of shelter for electrical and other sensitive equipment or displays. Temporary structures may not be used outside designated camping areas for living accommodation activities such as sleeping, or making preparations to sleep (including the laying down of bedding for the purpose of sleeping), or storing personal belongings, or making any fire, or doing any digging or earth breaking or carrying on cooking activities. The above-listed activities constitute camping when it reasonably appears, in light of all the circumstances, that the participants, in conducting these activities, are in fact using the area as a living accommodation regardless of the intent of the participants or the nature of any other activities in which they may also be engaging.

But the Pentagon would certainly be stretching the definition of “temporary.” Azerduy says the hydroponic greenhouse inside—-to be irrigated by runoff from the roof—-is meant mostly for growing tomatoes when the spring comes. I point out that that’s a good three months from now.

“Yeah, I mean, nothing is really permanent,” she replies.

At around 4:30, a building inspector came through, took a quick look at the structure, and posted orange “DANGER” signs on the plywood (there were apparently several code violations). So we may not see the architectural imagination of Occupy DC come to fruition.