You don't usually associate power plant with fun, but that's exactly what Tim and Jan Edler of architecture and design studio Realities:United had in mind.
Behold the Big Vortex, a waste-to-energy power-plant for Copenhagen that doubles as a ski slope, complete with a smoke ring generator to remind people about CO2 emissions:
Each smoke ring, approximately 30 meters in diameter and 3 meter in height, constitutes exactly one ton of fossil carbon dioxide, which is added to the atmosphere. This way the rather abstract pollution aspect, gets somewhat more graspable and understandable, something you can see and relate to.
The smoke rings are spectacular and highly esthetical, but linked to a controversial theme at the same time.