One of the highlights of the year in Tarragona are without doubt the Festes de Santa Tecla, which in 2018 are celebrated between Friday 14th and Sunday 23rd September.
The ten-day-long festival in honour of the Saints Day of Santa Tecla, the city's patron saint, draws massive crowds and one of the main attractions are the two Castellers day on the First Sunday and on Santa Tecla on September 23rd.
These Diades Castelleres are two of the main events in the annual Castells calendar and draw some of the best colles or groups of Castellers from around Catalonia.
Other interesting events are the Mostra de Folklore Viu which is normally on the First Saturday, and the procession of the Seguici Popular
However, over the ten days there will be something in the region of 450 events, including concerts by major bands, so there's always something for everyone.
The Festes de Santa Tecla de Tarragona were declared a Fiesta de interés turístico nacional by the Spanish government in 1996 and are considered a Festa patrimonial d'interès nacional by the Generalitat of Catalonia.
You can consult the Full Programme on the Official Santa Tecla Tarragona website.