The objective of the Clavius on the Web project is to increase the value of a part of the manuscripts preserved in the historical Archive of the Pontifical Gregorian University. The project examines some manuscripts relating to Christophorus Clavius (1538-1612), a Jesuit mathematician and astronomer.The manuscripts are digitized, transcribed, translated and analysed from the linguistic, lexical and semantic points of view. The terminology and domain entities identified in the text are structured in a lexicon and a ontology as well as linked to resources already available in the Internet in conformity with the Linked Data principles. Their visualization in the Web is implemented through Data Visualization techniques. The former are based on the correspondence among texts, translations and images, while the latter have the aim of displaying the content of the analyses, with a particular emphasis on the surfing of the lexical and ontological resources produced during the various phases.