The Feast of San Antón, in which the Brotherhood of San Antonio Abad, after Mass and the procession of the saint, invites the whole town to a get-together, lighting a bonfire in the square while people sing and dance in circles. Aniseed bread rings are handed out from house to house, and the rings on the staff of the effigy of San Antón are likewise renewed. 

Today's Real Feria de San Mateo stems from a privilege granted to the city by Charles II, dated in Madrid on 16 March 1688. It has always been held around 21 September, the saint's feast day, although the exact date has shifted over the years to fit in with nearby fairs and, more recently, to make use of weekends and cause less disruption to working life.

Although originally an exclusively agricultural and livestock event, over the centuries, as this activity lost importance, other elements have grown in prominence, such as trade, industry and entertainment at the fairground, based on rides for children and adults, and on public, institutional and private stalls. Livestock is still present, especially sport horses.