Save the date! La noche de los museos is going to take place again this year on Saturday, November 10, 2018.
Over 200 museums will be open from 8PM and until 3 AM with free admission and free public transport on some bus lines and the subte. You can check the location which were open in 2017 here by name and here by neighborhood, while waiting for the 2018 list (like to be the same) which has not yet been disclosed.
More info: http://www.buenosaires.gob.ar/…e_de_los_museos/index.htm