We had "friends" while living in Buenos Aires ... the sort that are friendly when they see you but then .. not. But when they were friends, they invited us to lunch and to visit and to see their apartment.
They bought it from a man who had great style and talent in turning an old apartment full of many rooms and sort of dowdy and fusty into a palatial apartment that I wanted soooo badly.
But they bought it privately and I never knew it was even on the market and they did a lovely job with it .. making it less fabulous and more homey...but fabulous.
This is the staircase to the apartment. There is one apartment per floor. You see what I mean ?
It shoulda been mine !!
It is a good start, find a building with a grand staircase and then decide on an apartment.