Hellmouth or Boca de Inferno is a blowhole located on the east coast of the island of São Tomé. It is not certain whether this geological phenomenon got its name because of the shape of the lava tube, which resembles a gaping mouth, or because of the surrounding volcanic rocks, which with their almost regular shape resemble huge teeth, or maybe, because of the sound that is created when waves hit Hellmouth. Probably all of the above influenced the name, and it certainly affects the huge number of visits by tourists.