Final answer:
Mammoth Hot Springs is the feature that lies outside the perimeter of the Yellowstone Caldera. It is located in the northern part of Yellowstone National Park, beyond the boundary of the iconic caldera formed by the Yellowstone Hotspot's supereruptions.
Step-by-step explanation:
Mammoth Hot Springs lies outside the perimeter of the Yellowstone Caldera. Within the context of Yellowstone National Park's geothermal features, the Yellowstone Caldera is a significant geological structure formed from past volcanic activity. The largest of several supereruptions from the Yellowstone Hotspot created this caldera, a depression in the Earth's surface caused by a volcanic eruption. The Mammoth Hot Springs, known for their intricate terraces formed from limestone deposits, are not within the caldera's limits. Instead, they are situated in the northern part of the park, beyond the boundary of the caldera, where heat from the Earth's subsurface continues to influence the area's geothermal activity.
Other geothermal features mentioned in the question, such as Castle Geyser, are found within the caldera's boundaries, while Fort Yellowstone and West Thumb Caldera are associated with the park's management and other geological features, respectively. The hydrothermal systems in Yellowstone, including the unique biology found in hot springs and geysers, are sustained by the residual heat of the Yellowstone volcanic system, indicative of the still-active hotspot beneath the park.