Once a year Buenos Aires joins other cities across the world in giving the general public access - over 48 hours - to normally restricted buildings or venues. This unique experience is really popular with locals and can get booked up quickly so make sure to book a spot in advance.
If you find yourself in BA September / October (normally the time when this event takes place) and are looking to peek behind some hidden doors in the city then check out Open House. The event is a great insight into some the city's most intriguing buildings e.g. "La Prensa", an old British newspaper office (pictured above).
Book in advance. Seriously. It's the one time when Argies aren't so laid back ;)