After fully exploring the Upper Geyser Basin, we made a quick detour to Biscuit Basin, just a short distance away. While it doesn't rival the grandeur of the Upper Basin, it offers a pleasant boardwalk loop around a handful of small geysers.
The bridge across the Firehole River into Biscuit Basin appeared to be guarded by a “fierce beast”, though it was far more interested in grazing than intimidating passing visitors.
Just beyond the bridge, we spotted Black Opal Pool, the only black hot spring we encountered in Yellowstone.
The main highlights here are Wall Pool (above) and Sapphire Pool (below). Wall Pool, averaging around 88°C, is intensely hot and even boils in places.
Sapphire Pool, slightly cooler at about 77°C, also bubbles intermittently. Their extreme temperatures support thermophilic bacteria, which create the vivid blue tones that dominate both pools. Each has been shaped by past explosive events, leaving behind steep, dramatic walls that enhance their visual impact.
Other minor features include Avoca Spring (above) and Jewel Geyser (below), which resemble some of the smaller geysers found in the Upper Basin.
As a tip for future visitors, Biscuit Basin is best explored before the Upper Geyser Basin, otherwise, it can feel a little underwhelming by comparison.
