Too often, we spend so much time focused on our devices or on the ground that we forget to take a look around when outside. The optical illusion below illustrates just how much we might miss by ignoring our surroundings.

The image below was submitted to Mighty Optical Illusions by Tony Ward, an illusion enthusiast who is constantly on the lookout for fun and challenging puzzles like this one. Apparently, the lush green tableau contains 13 faces hidden within the scenery, all waiting to be discovered.

Can you spot them all? Scroll down for the answers.

Are you ready? Here are all 13 faces, circled in red:

How did you fare? Did you manage to find all 13? Don't forget to share this visual puzzle with your friends!