Turkey Mountain Urban Wilderness Area is a 300-acre (121 ha) area of undeveloped land that stretches from I-44 to 71st Street in Tulsa, Oklahoma, United States. It is managed by the Tulsa River Parks Authority and open to the public. The main entrance to the wilderness area is at 67th Street and Elwood Avenue in West Tulsa.
Close to the river there are several markings in the stone, one of which seems simply to be the letters "PIA". These were believed by writer Barry Fell (Wikipedia page ) to be petroglyphs left by pre-Columbian European travelers. The idea of Pre-Columbian trans-oceanic contact by Europeans, apart from the Vikings in Newfoundland, is considered a fringe theory or pseudoarchaeology.
More information on the Wikipedia page