This area is situated around Old Faithful and contains perhaps the most exciting range of thermal areas to be found anywhere in the park. These can be explored by two boardwalk loops, each of which will take over two hours to complete. The main feature is of course Old Faithful, which erupts approximately every 80 minutes. The times of the next eruption can be found in Old Faithful Lodge. This geyser can erupt up to an average of 130 feet and eruption last from ½ to 5 minutes. It has been erupting as regularly as clockwork since 1870.

The next most impressive geyser is Castle Geyser that erupts with water and steam. It can shoot water as high as 80 feet into the air and lasts for as long as 30 minutes followed by more than an hour spouting steam. As it changes from the water phase to the steam phase it is at its most impressive.

A short distance from this is the splendid Grotto Geyser, which spumes water and steam from the many holes in the cone. It is a very noisy geyser, which is almost continuous. A short walk from here is Riverside Geyser, which is situated on the east bank of the Firehole River. This erupts with a 75 feet column that falls into the river. It erupts approximately every 6½ hours.