The oldest church in continuous service in Argentina sits on the west side of Plaza San Martín. Begun in 1577 and finished in 1758, it shows the slow accretion of styles you would expect of a 200-year project — a Romanesque-leaning base, Baroque flourishes, neoclassical statuary out front, and a notable dome above.
Inside, the gilded altarpiece and the angels with indigenous Andean features in the ceiling frescoes by Emilio Caraffa are the highlights. The cathedral also holds the remains of several colonial bishops and the patriot José María Paz. Entry is free; modest dress expected.