The Italian city that hosted the 1951 meeting where Watson saw Wilkins present DNA X-ray data was Naples.
Maurice Wilkins had already obtained promising diffraction photographs from highly ordered DNA fibers at King's College London. At the 1951 conference in Naples, one of those images helped convince the young James Watson that DNA had a regular molecular structure worth pursuing. Watson later described the encounter as a turning point that intensified his interest in DNA.
The Naples presentation came before the famous Photo 51 episode. Photo 51 was produced in 1952 by Raymond Gosling while working with Rosalind Franklin at King's College; Wilkins later showed it to Watson in early 1953. Thus Naples is associated with Watson's first important exposure to Wilkins's DNA diffraction work, while Photo 51 belongs to the later stage of the discovery.
Naples is sometimes confused with Cambridge or London because Watson and Francis Crick built their model at Cambridge, and the crucial experimental work occurred largely at King's College London. The three scientists later shared the 1962 Nobel Prize in Physiology or Medicine.