The day of Saint Felix is celebrated on August 30 in Vilafranca del Penedès, since the beginning of the 19th century. The castle day is one of the most important events of the Vilafranca Major Festival, considered a 'patrimonial festival of national interest' by the Generalitat de Catalunya. It is celebrated in the Plaça de la Vila de Vilafranca, considered "the most castellar square", in large part, because of the memorable days of Sant Fèlix that have been seen there.

Sant Félix's day is the only one that is celebrated on a fixed day (whichever day it falls on) and that has the presence of groups invited from outside the town. The day of Sant Fèlix is the most important castellera performance in the calendar, as the four best gangs in the castellera world at the moment take part. On August 30, in Plaça de la Vila, you can see the best castells of the season, in a framework of historic rivalry between the gangs that gather there.

The best performance ever performed on a Saint Felix Day took place in 2017, where the Castellers de Vilafranca equaled the best performance in the history of the castells unloading the 3 of 10 with lining and handcuffs, the tower of 8, the 3 of 9 with lining and the needle and pillar of 8 with lining and shackles.

The Castellera day is surrounded by a set of events from the first hour, with the matinees through the streets of Vilafranca, the going to office, the pillars at the Als Castellers monument, the entrance to the square and the evening procession (with the entrance of Sant Felix later).

The gangs that have participated in the Sant Fèlix day for the most years have been the Xiquets de Valls (currently, the Colla Vella and the Colla Joves), the Castellers of Vilafranca and the Minyons of Terrassa. Even so, the Nens del Vendrell, the Colla Jove Xiquets de Tarragona, the Xicots de Vilafranca, among others, also participated.