We visited the Casa Rosada.
For historic locations, Castelar Hotel, 1929. Frequented by poet Federico Garcia Lorca and writer Jorge Luis Borges
Café Tortoni, 1858, oldest cafe in the city.
Crypt of San Martín, liberator of Argentina and other countries in the Metropolitan Cathedral
San Ignacio de Loyola, oldest church in Buenos Aires, 1830
Feria San Telmo and Pasaje de la Defensa were nice to walk around
El Gran Ateneo book store
Cartoon character statues along Calle Defensa between Calle Chile and Plaza de Mayo.
A couple old bars/restaurants we enjoyed, Plaza Dorrego Bar, 1880, and Bar Federal.
Recoleta cemetery was interesting and has additional prominent graves other than Eva Perón. We thoroughly enjoyed La Boca area, but visited it during daylight hours. We stayed in the San Telmo area and ate at restaurants in that area.