Located in Parque Lezama is the city’s national historical museum. It’s mostly dedicated to Argentina’s revolution of May 25, 1810, though there is some coverage of pre-colonial times. There are several portraits of presidents and other major figures of the time, along with a beautifully lit generals’ room. Peek into the re-created version of the bedroom of José de San Martín’s – military hero and liberator of Argentina (along with other South American countries).
Highlights include an Argentine flag taken by General Belgrano to Alto Perú (now Bolivia) in 1812 and, best of all, a sword belonging to San Martín himself, now guarded by grenadiers; you'll need to walk through a tunnel displaying other revolutionary heroes' swords, lit up like a nightclub, to reach it.