In this paper we show how the investment in cultural events may encourage the building of social cap-ital and foster the development of local communities. We rely on a case study we conducted on thesocio-economic impact of "La Notte della Taranta" Festival, one of the most important European festivalsdedicated to traditional music (about 170,000 participants per year), on the sub-region of southern Italywhere it is held. Our evidence is based on a large survey, consisting of nearly 10,000 interviews to Festivalattendees over a span of five editions (2007-2011). A primary result is that the initial economic invest-ment in the Festival has brought a short-term return in terms of touristic attraction worth more thantwo times as much. More importantly, our results indicate that a cultural festival, despite being a massgathering, is able to create strong bonds among its participants and between them and the area wherethe event takes place. Although these bonds are "instantaneous", i.e. temporally restricted to the durationof the event, they are positively correlated with the economic impact of the event on the territory.