“Are you sure you want to be dropped off here?” the cab driver asks me on Friday night as he pulls over on the corner of Michigan Avenue and 1st Street NW.

Seeing a stream of people with arms full of supplies walking towards construction equipment that lines a chainlink fence, I know I’m in the right place. A portion of the fence that protects the McMillan Sand Filtration Site from outsiders has been cut so that revelers can make their way into one of the vaults that comprises the former water treatment plant.

It’s time to take the protest underground with “Existence is Resistance.”

D.C. activist Adam Eidinger and anti-imperialist organization Code Pink planned the event in honor of Ariel Vegosen of Code Pink’s birthday. She travelled to Palestine, Turkey, France, Italy, Greece, and then back to Palestine before returning stateside on Friday.

For Vegosen, the festivities were a way to culminate her time abroad, and draw connections between global struggles, whether “Palestinians working every day to overcome occupation” or the planned development of McMillan Park. “Our existence here is a form of resistance,” she says of the party’s location.

Many of the people in attendance were old pros of setting up movable feasts in the sand, thanks to their time at Burning Man. They quickly morphed the underground vaults into a stunning scene for a celebration. Organizers unfurled strings of lights, lit candles, and set up a flame-filled bar and a car battery-powered DJ booth, as well as a donation box for Friends of McMillan Park.

Chris Otten of the Save McMillan Action Coalition points to Chicago and Seattle as cities that are choosing to preserve their underground history, and says that D.C. should do the same with McMillan. The sand filtration site was built in 1905 and has sat unused since the 1980’s, other than tours which ended in 2012.

Eidinger thinks that the northern strip of McMillan could be a “world-class venue” for concerts and other events, easily recouping for the city whatever money would be spent on fixing it up.

During public hearings, developers have made the case for converting the more than 20 acres into a mixed-use property. But the controversial project has faced some stumbles, as when D.C.’s auditor called the process for finding a developer “flawed” this fall.

Friday’s protest of the development got busted by the police, who were called to the scene by nearby security guards. Eidinger says that at first, officers planned on arresting the 100 or so people in attendance. After explaining that the gathering was a protest and sticking around to clean up, though, no arrests occurred. Organizers are now plotting novel ways of protesting development of the site, after throwing parties this weekend and last year in the vaults.

Before officers showed up, the smell of smoke in the air was thick, and the attendees had a larger per-capita number of fire jugglers than I’ve ever seen in this city. “It’s important to celebrate and bring joy to the movement,” says Vegosen.

One participant agreed. “I care about all kinds of issues,” he said. “I’m here to party.”