The Land of Forests (森の国, Mori no Kuni) is a country full of forests, which makes the river the only crossing access. The criminal group Shinobazu is acting around in this country. Gantetsu, who was a member of Shinobazu was captured and was supposed to be brought to the country's capital for a trial. He never made it however, as the ship was attacked by the Shinobazu. He "escaped" and, along with Naruto Uzumaki and another they managed to defeat the Shinobazu. In the end, Gantetsu's name was cleared.
It is also suggested in the anime, that Hashirama Senju and the Senju clan were also initially from the Land of Forests.