Mantle's Cave is a large rock shelter in the Castle Park area of Dinosaur National Monument in northwestern Colorado and one of the region's most important archaeological sites. Though its size made it a conspicuous shelter, archaeologists concluded that its cool northern exposure and elevation made it poorly suited to long-term living. Excavations in the 1930s and 1940s uncovered dwelling sites, granaries, pottery sherds, baskets, hunting tools, cached objects, and a bag with a feathered headdress and beads. No human remains were found, and investigators judged that the alcove was used chiefly for storage. Its remains are especially important for understanding the Fremont culture and its connections to later Ancestral Puebloans.