The Cathedral of Saint Thekla is the most significant and famous monument of Tarragona. The construction of the cathedral began in 1171 on the site of the ancient Roman temple of Jupiter, which first replaced the Visigothic temple, and later the mosque. The cathedral was consecrated in 1331, while still unfinished, construction was completed in 1350. The architects of the cathedral were Raymond de Mila, master Bertomeu and Guillem Clergue.

The architecture of the apse bears the imprint of the Romanesque style and resembles a fortress in outline. In the eastern part is the Diocese Museum with a large collection of carpets, numerous wrought iron products, ceramics, coins, old manuscripts and other valuable items.

There are fifteen bells in the bell tower of the cathedral, some of which are among the oldest in Europe, in particular the Asumpta bell was cast in 1313, and the Fructuosus bell in 1314.