Grand Prismatic Spring

Grand Prismatic Spring - Yellowstone NP A section of the 1/2 mile walkway that parallels part of Grand Prismatic Spring is shown here. This spring is actually a huge oval pool 370 feet across and 120 feet deep surrounded by unusually colorful bands of algae and travertine terraces with wavy run off channels, giving the appearance from above of a giant star. This pool constantly steams and bubbles with hot mist which blows in the breeze making it hard to see the pool itself.