The cathedral rises beside the Cabildo square, just a step from the bay. Its sober, white neoclassical façade hides a high altar clad in silver and a carved, polychrome altarpiece that came from the old Franciscan convent. It is the city's mother church, dedicated to its patron, the Virgin of the Assumption. Near the cathedral, the Monseñor Juan Sinforiano Bogarín Museum holds religious art and objects from the history of the Paraguayan Church.

The first church, made of wood and mud, went up in 1539 and burned down in the fire of February 4, 1543. The cathedral was established on January 10, 1548, as the seat of the first bishopric in the Río de la Plata region. The current building was constructed between 1842 and 1845 under the government of Carlos Antonio López, to a design by Pascual Urdapilleta, and was blessed on October 27, 1845.