Yellowstone Lake is huge. It is the largest high-altitude (above 2,130 meters, or 7,000 feet) freshwater lake in North America, covering about 341 square kilometers (about 130 square miles). That’s about 100 times the size of New York City’s Central Park! Over the past decade or so, researchers have discovered many new features on the lake bottom, including a vigorous hydrothermal system that would make for an impressive geyser basin if it were on land. In fact, the hottest hydrothermal vent temperatures measured anywhere in the Park were on the lake bottom — 170°C (340°F). What else might the lake be hiding beneath its surface?