Architecture has hardly been the focus of Occupy Wall Street and its affiliated protests around the nation. But a barnlike structure erected in McPherson Square—a small national park in downtown Washington, D.C., where Occupy D.C. protesters have staged a standing protest for two months—became the focal point of a standoff with police on Sunday that lasted more than nine hours.

Early Sunday morning, protesters erected a structure on the park’s empty south lawn, an area of the park that had been previously free of tents, as it is favored by ducks. The barn was incomplete as of dayrise, but the protesters had completed the frame for the nearly two-story structure.

The United States Park Police, who has jurisdiction over the McPherson Square park, called a building inspector with the National Park Service to perform a building inspection. On Sunday afternoon, the inspector declared the unit dangerous, and police warned the protesters to evacuate.

On Sunday evening, a scene unfolded in which police parked an armored personnel carrier next to the structure and inflated a moon bounce on its other side to catch protesters leaving the barn roof. As horse-mounted police stood watch, police on foot arrested dozens of protesters inside the structure. Six protesters remained on top of the barn, challenging police to retrieve them by using a cherry-picker to reach the protesters. While most of the protesters complied at that point, one last protestor clung to the barn’s A-frame structure for hours.

Police had arrested all the protesters by 9:00 p.m. on Sunday night and dismantled the barn later in the evening. Ann Wilcox, an observer from the National Lawyers Guild, said that police understood the structure to be a demonstration of civil disobedience and that the charges against the activists were unlikely to be severe.

The larger tent camp remains—raising questions about the purpose and use of parks and the structures that are ostensibly allowed on them.

A nearly two-story unit, the makeshift barn was built to serve as “an emergency winter shelter,” according to a man named Paul who claims to have purchased materials and directed the construction. Occupy D.C. protesters intended to hold general-assembly meetings there. The roof was to be covered in clear plastic sheeting in order to foster a greenhouse effect. Some 30 to 40 people helped in the assembly, according to Paul, using prefabricated shed materials purchased from Johnson Lumber, a local lumber company.

He called it “the People’s Pentagon,” referring to the pengaton shape of the barn’s gable end. “It was a place to meet and have real democracy,” he says.

The Occupy D.C. demonstration is one of a few remaining camps that has not been taken down by authorities. Though there were a few reports of minor injuries from Sunday’s standoff, the confrontation between Park Police and Occupy D.C. activists held little resemblance to the raids in Oakland, Calif., at the University of California at Davis, and at Lower Manhattan’s Zuccotti Park—the home of the original Occupy Wall Street protest.

Perhaps owing to the unique nature of Washington’s parks and municipal system—the city’s Metropolitan Police Department does not have jurisdiction in McPherson Square, so the mayor cannot order their ejection—the protest movement here may last where others have been forcibly disrupted. Park Police showed no sign on Sunday that they would order the removal of dozens of tents that remain in the park.

The activists appear to be considering buildings and their uses more generally as the subjects of the malleable Occupy protests. On Nov. 19, protesters affiliated with the Occupy D.C. camp seized the historic Franklin School building, a former homeless shelter in downtown Washington. Eleven were arrested after the “Free Franklin” group unfurled a “Public Property Under Community Control” from the building’s roof.

Given Washington’s Indian summer weather, a standing protest has been possible even into December. With winter looming, though, protesters appear to be looking to solutions to stay safe in severe cold. At the same time, the National Park Service has warned the protesters that while tents for symbolic purposes or to accommodate first-aid services count as uses consistent with First Amendment rights, camping is prohibited. As the protest has worn on, though, protesters have erected superstructures, including tarps over groups of tents, and culminating in the barn structure.