TBWA Milan created a billboard installation that literally opened a window on the world. Set up in Milan for Airbnb, three open windows showed passersby views of three different travel destinations. In fact, the windows were connected to real Airbnb houses. Other windows were closed, but pedestrians were invited to open them by pushing a big red button. Sometimes they hit a blank wall - but luckier participants saw a great view and were told they had won a digital travel coupon from Airbnb. During the campaign, one person participated every 40 seconds.