Research Cave - Credit: Wikimedia Commons
Research Cave - Credit: Wikimedia Commons
Research Cave, also known as the Arnold Research Cave and the Saltpetre Cave, and designated by the Smithsonian trinomial 23CY64, is a major Native American archaeological site near Portland, Missouri. Investigation of the site has uncovered evidence of human habitation as far back as 8,000 years. The site was designated a National Historic Landmark in 1964; it has been recommended for de-designation due to looting. Read more on Wikipedia
Source: en.wikipedia.org