Dinner Under the Helsinki Sky 2013. (Lauri Rotko / Visit Helsinki via Helsinki This Week)

What happens when you invite an entire city to dinner? If the city in question is Helsinki, you might find yourself setting a table for 1,000. That is what happened in 2013, when Yhteismaa (Common Ground), a Finnish non-profit dedicated to participatory city culture and placemaking, hosted the first Dinner Under the Helsinki Sky on Helsinki Day (June 12). “We were thinking about how we could celebrate Helsinki’s birthday,” recalled Yhteismaa founder Jaakko Blomberg. “We thought of eating together: that’s what you do when you’re celebrating.” The inaugural event—which was fully booked online within two and a half minutes—took place at a quarter-mile-long communal dinner table set in the middle of Pohjoisespladi, a prominent urban thoroughfare. Participants brought their own food, drink, and utensils to dine with friends and strangers in the middle of the automobile right-of-way.

Dinner Under the Helsinki Sky has since become an annual tradition and inspired spin-offs in other cities including Jyväskylä and Espoo. Yhteismaa—whose other projects include Cleaning Day, Parking Day, and the Home Theatre Festival—also coordinates a global version of the event. Dinner Under the Sky—Everywhere, which takes place annually in August, encourages Helsinki residents to recreate the founding event, guerrilla-style. Groups of friends and neighbors set up family-style dinners in a variety of outdoor spaces, including private yards and public parks, and crowdsource a map of dining locations. Yhteismaa offers support in the way of table and chair rentals at nominal cost.