There’s some confusion about the World’s Tallest Fountain. What used to be the World’s Tallest Fountain in Fountain Hills has been usurped by the Gateway Geyser in East St. Louis, Illinois, but the Arizona gusher is still the World’s Tallest Fountain sometimes. The Illinois fountain shots a geyser 627 feet into the air, the best the one in Arizona can do is 560 feet, when operating at full capacity.