Invasion of the giant spiders:

It’s the stuff of nightmares for arachnophobes: Giant eight-legged creatures, crawling over the rooftop of a building, seemingly waiting to pounce on their next victim. But this is no arachnid invasion. It’s an optical illusion so realistic it’s enough to make the bravest soul’s skin crawl. These images painted on top of a warehouse in Seattle of harvestman arachnids – otherwise known as a Daddy Long Legs – seemingly spring to life when viewed from a particular angle.