Several Chicago buildings will go dark Saturday night for Earth Hour.
At 8:30 p.m. Chicago time, millions of people around the world will switch off their lights for 60 minutes.
Earth Hour is the largest environmental event on the planet.
The City of Chicago, ComEd, The World Wildlife Fund, and Sony Pictures will celebrate the event at the Chicago Cultural Center, in Preston Bradley Hall.
Superhero Spiderman will also be there!
The party begins at 6:30 p.m.