I hadn't seen old faithful in many, many years since my childhood days. Truth be told, it's still just as impressive today as it was back then. With todays technology, you don't even have to visit there to watch it erupt, although it's much more impressive in person than on a web cam.
Old faithful gets its name from its punctuality and predictability. Old faithful erupts almost every 90 minutes. It shoots approximately 150 feet up in the air, not to mention the four to eight thousand gallons of water that is released. The eruption lasts around 3 to 5 minutes. The cause of these eruptions is due to geothermal vents due to the huge caldera that Yellowstone sits on, which encompasses 1,530 square miles.