Hell’s Half Acre, that’s the name Rudyard Kipling gave to the Midway Geyser Basin when he visited Yellowstone in 1889. Midway has two of the largest (and most colorful) hot springs in the world: Grand Prismatic Spring and Excelsior Geyser, seen in the picture below.
Excelsior Geyser erupted some 300 feet high before the 1900s and was then the largest geyser in the world. It is now dormant and considered a hot spring, discharging more than 4000 gallons of boiling water per minute. The water is 199F (93C)!
You need to walk past this spring to get to the Grand Prismatic, which is perhaps more popular with tourists today. As a result many people hurry by and don’t pay too much attention to this beautiful and colorful spring. The water has this amazing, intense blue color as you can see here. Various vents boil and churn up the water covering it, almost perpetually, in a blanket of steam.