The first time you see prayer flags backlit by the sun you do think they're magical. You wonder who hung them and you wonder what messages they sent into the breeze. The more there are the more you feel like you're somewhere special. Somewhere super charged.
I spent my days in Nepal looking for prayer flags. If you looked out into the hillsides you could often times see canopies of them indicating a monastery. If you were walking down the streets in Kathmandu you'd find them strung in the most random of locations. If you went to a temple you could walk directly under them and watch them flap.
They're as elemental as their colors indicate. Sky, Wind, Water, Fire and Earth. The Tibetans believe that the mantras on the flags will be carried by the wind to promote good will and compassion. I believe it too.