At the theatre darling
Why locals love it
This is admittedly a tourist hot spot but for good reason; outside and inside of Teatro Colon is somewhere that just has to be experienced when in Buenos Aires and I would really recommend getting tickets to see a show so you can enjoy it in all its glory. I saw the ballet "Gisele"(from the higher and cheaper seats) and it was mesmerizing.
Why you should visit it
A ticket to a show at Teatro Colon is a bit of a steal when comparing it to other famous theatres across the world so it's your once chance to indulge in a bit of upper class culture. There are even some performance you can go along to for free or for very cheap. The architecture is stunning and performances are world class.
Buy tickets at the start of the month for a fraction of the price. Tours of the building are also available if you're not able to make a show.