I am native from Minas Gerais and I have always listened the craziest stories about this town. But I have to admit that it is the first time I hear about this tunnel connecting to Machu Pichu. As far as I know, Sao Tomé is well known as a destiny of hippies and people that believe in magic, ETs and other supernatural things. In fact, most of people go to this town and take drugs expecting to see anything "different". I remember that my uncle has a sticker of this city written Sao Tome das Letras with a little witch on it. However, I do believe that any story might have at least something of real. On this site there is a small picture of the cave, Gruta do Carimbado. It is also written that many believe in the existance of several tunnels on America converging in Machu Pichu. There's also another famous place there, called Ladeira do amendoim (peanut hill), where compasses get crazy and havy cars with their motors turned off climb this hill like if they were attracked by a magnet.