Created by Rem Koolhas, it is surely a must-see in Porto.
It holds a huge variety of events, not only music-related: from classical to dancefloor music to architecture conferences. High quality guaranteed!
Guided tours to the building are available (only for groups), and most of the events have special prices (for under 25 year-olds, for example). I totally recomend the guided tour, because it is very unique building, and this way one can look at it in a very different way than before