There is very little relicts to be found in tango history. Most of the important things of sounds, steps, atmosphere and words do dissappear when completed. Therefore this peace of archaeological excavations feels so interesting.
Café de Hansen opened the doors 1877 and were hosting the tango visitors to 1912. There is discussions about the information if people were actually dancing there or if they just listen to the music while eating and refreshing themselves.
You find a more detailed story in the Tango Chamuyo blog - better English is it too!
The Spanish version here: