The volume presents the critical edition – provided with an introduction, an Italian translation and a commentary – of the main medieval and humanistic treatises concerning the thermal springs of Viterbo: the four redactions of the treatise De Viterbiensibus balneis, by the physician Girolamo da Viterbo († 1395); an excerpt contained in a treatise attributed to Gentile da Foligno; the didascalic poem in exameters De thermarum Viterbiensium virtutibus, by Evangelista Bartoli from Viterbo (ca. 1515).