Secrets of the Viking Stone

I have enjoyed the show. As a kid in MN, with an uncle in Bismarck, ND I got to see a mandan earth lodge. Shaped similar to a viking long boat upside down. The boats the Mandan's used for fishing were said to be similar to Celtic round boats. Some of the first settlers said the Indians spoke a language similar to Galic. Since the Mandans have disappeared, as far as I know, it may be interesting additional research. Mapping the rivers of MN, SD, and ND may give a clue to exploration from anchorages in Lake Superior. (Drill holes in big rocks).