 The fountains use over one million LEDs . The inner surface of each tower uses 147 smaller screens with a total of 264 @,@ 480 LED points ( each with two red , one blue and two green LEDs ) . The physical demands of LED screens , in particular the red , green , and blue long @-@ life light bulbs and the <unk> <unk> , created three major challenges : supporting the physical structure , combating heat buildup , and <unk> <unk> of the display . Plensa had used LED fixtures on previous projects , and thus had some experience with these issues . The LED structure is not supported as a single wall ( which would be 50 feet ( 15 m ) high ) , but rather as several segments that are noticeable as visible horizontal bands every few feet : these show where the LED equipment is supported . The heat generated is handled by fans that cool the air at the bottom , that then works its way through the chimney @-@ like tower . <unk> was determined to be optimal with LED lights 2 inches ( 51 mm ) behind the glass . 
