At Avenida Rivadavia and San Martín, the cathedral occupies the site of the original colonial church designated by Juan de Garay in 1580. It opened in 1836; Joseph Dubourdieu’s 1862 bas reliefs on the pediment compare the biblical reconciliation of Joseph and his brothers with the battle of Pavón, where Bartolomé Mitre’s Buenos Aires forces defeated caudillo Justo José Urquiza.

Within the cathedral, a lateral chapel holds the Mausoleo del General José de San Martín, the independence hero’s tomb. Disillusioned with post-independence turmoil, San Martín lived in exile in Boulogne-sur-Mer, France, until his death in 1850; his remains were returned to Argentina in 1880, after President Nicolás Avellaneda ordered construction of this elaborate crypt, marked by an eternal flame.