The Permafrost Tunnel was excavated into a man-made escarpment, and is approximately 110 meters in length, 2 to 2.5 meters high, 4 to 5 meters wide, and 15 meters below the surface. The tunnel is composed of two portions: the adit (horizontal passage), which passes entirely through frozen silts, and the winze (inclined adit), which extends off of one side down 45 meters passing through silts, a gravel layer, and then into bedrock.
Engineers originally used the tunnel to evaluate underground excavation techniques in permafrost. Visible throughout the permafrost are a diverse assemblage of animal fossils and plant remains. Beatles, mites, flies, moths, butterflies, and snail shells are all frozen in time. Bones and teeth of bison, mammoth, and horse are among the vertebrate fossils that are visible.
I believe they do tours every once and awhile, but this is a very interesting place that I would recommend checking out after grabbing the cache. Cache is relatively easy and has all year long accessibility.