The Cathedral of Santa Maria Assunta in Rieti, the most important church in the city, is located in the highest part of the historic center and is listed as a national monument. Today's Cathedral was built in the 13th century, but there is evidence of a previous place of worship as early as the 6th century; the original style is Romanesque but over time there have been several Baroque additions. The main facade consists of a portico and an impressing bell tower that overlooks the main square of Rieti.
Between the 12th and 13th centuries the church was often chosen as main “branch” by the Pope and was therefore the scene of important historical events such as the canonization mass of San Domenico, founder of the Dominican order, celebrated by Pope Gregory IX, and the coronation of Charles II D'Anjou to King of Puglia, Sicily and Jerusalem at the hands of Pope Nicholas IV.