Calva is a traditional sport played in certain parts of Spain. It has roots going back to pre-Roman times, being developed by the Celtiberians who lived in the modern-day provinces of Ávila, Salamanca, and Zamora. It was a game for shepherds, who threw stones at bull’s horns to entertain themselves. With the passing of time, the game was modified: a piece of wood (the calva) came to be substituted for the horn, and the stone was replaced with a cylinder of iron or steel (the marro). The name of calvawas derived from the field in which the game came to be played, which was free of obstacles and rocks. *Today the sport is practiced mainly in Castile, Salamanca, Zamora, and Biscay, although also in Madrid, Barcelona, Plasencia and Navarre.