Named Yampah Springs—meaning “Big Medicine”—by the Utes, this pool was created in 1888 when enterprising developers diverted the course of the Colorado River and built a stone bathhouse. The springs flow at a rate of more than three million gallons per day, and, with a temperature of 122 F (50 C), they’re one of the world’s hottest springs. The two open-air pools together are nearly two city blocks in length. The larger pool, 405 feet by 100 feet, holds more than a million gallons of water and is maintained at 90 F (32 C). The smaller pool, 100 feet long, is kept at 104 F (40 C). There’s also a kiddie pool, two waterslides, plus a restaurant, sport shop, and miniature golf course. Suit and towel rentals and coin-operated lockers are available. The Spa of the Rockies offers massages and a full menu of other treatments. Allow 2 hours.