The famous Senate Square in the center of the Finnish capital is surrounded by government buildings, the university, the cathedral and the Sederholm House. The players' task is to design pavilions across the square to protect pedestrians in the rain. Helsinki is based on the design of Copenhagen by the same design team, but with some added complexity.

Players score points for completing rows and columns in a Tetris-style tile placement, and the player with the most points at the end of the game is the winner.