Lake Lahontan is a large, ancient lake that existed during the last Ice Age, approximately 12,000 to 15,000 years ago. It was located in what is now Nevada and parts of California. The lake was formed by melting glaciers and covered a significant area, making it one of the largest lakes in North America at that time. Today, remnants of Lake Lahontan can be seen in the form of smaller lakes, such as Lake Tahoe and Pyramid Lake. The lake's history is important for understanding the region's geology and climate changes, as well as the ecosystems that developed around it.