|Plantgreenideas.com and their giant heads on Michigan Avenue|
These look pretty creepy to us, but the message is positive. According to their website plantgreenideas.com:
Plant Green Ideas Chicago 2013 is a never-before-seen interactive art installation intended to inspire new ways of thinking about sustainability and to encourage new behaviors that will positively impact the environment while also raising awareness of Chicago’s leadership in the “green” economy.
(Hat tip: CD & LH!)