It’s that time of year again.

Tomorrow, Saturday March 27 marks the arrival of Earth Hour, the World Wildlife Fund’s climate change awareness campaign. To participate, just turn off the lights for an hour starting at 8:30 pm. That’s it.

The beauty of the project is not in the hour’s worth of energy savings, but in how plunging some of the world’s most recognizable landmarks, modest homes and entire neighborhoods into (near) darkness gets the message across. Low tech, but high impact.

Learn more at My Earth Hour and check out the cool slideshow from last year’s Earth Hour after the break.