Imagine this: On an early summer night, just after sunset, you join tens of thousands of your neighbors to become a living urban canvas. You wander from a storytelling bonfire to a luminary promenade, from a huge LED screen with an original arcade game to a dance party. As the sun rises, you hop on your bike to head home. It's not a happy dream, it's Northern Spark, the overnight art festival that kicked off in 2011, returned in 2012, and this year will spread its collaborative energy across the river and take over St. Paul's Lowertown neighborhood on June 8, beginning at 8:58 p.m. The institutions surrounding the participants will switch from the Walker Art Center and MCAD to the Union Depot, Bedlam Theater, Twin Cities Public Television, and the Minnesota Museum of American Art, but the revelers and their revelry will be much the same, buoyed by more than 80 art events and ambient camaraderie into the dawn.