Porto's long-awaited Casa da Música by OMA is finally due to open later this month. First conceived as part of Porto's celebrations for the European City of Culture in 2001, political wrangling and difficult site conditions conspired to delay the project. Now the finishing touches are being applied to a building that has come to be known as Porto's Guggenheim, for the way in which it attempts to raise cultural and architectural profiles and put this industrious but not especially touristconscious city firmly on the short-break map.
Home to the Porto Philharmonic Orchestra, the Casa da Música is also intended as an equally accessible forum for rock, jazz and experimental music. Though the building resembles a deformed lump of concrete, its bold architecture aims to demystify and democratise concert-going. The form was generated by notions of carving out spaces from a solid mass, and the outcome is a 400mm-thick faceted concrete shell, which supports and ties the building together, and acts as an internal stiffening diaphragm.
Arup, under the direction of Cecil Balmond, masterminded the structure. Exposing raw concrete to Porto's notoriously wet climate might seem to be asking for trouble, but the concrete used incorporates a special coating and clever panel jointing to throw water off the surface.
Poised on its windswept plaza like a monumental meteorite, the Casa's daunting mass is an uncompromisingly contemporary addition to a 19th-century neighbourhood. Inside, however, things are more fluidly informal. The main auditorium seats 1,300 and though OMA sought to escape from the 'tyranny of the shoebox hall', it had to concede that the shoebox still has the best acoustics, so set about trying to re-envisage a traditional type for the 21st century.
The most dramatic move is to take away the back and front walls of the hall, creating proscenium arches infilled with corrugated glass panels.
These giant windows frame views out over the city, transforming what is usually a hermetic interior into a luminous space that explicitly connects building with city. Huge net-like blinds made by Dutch designer Petra Blaisse can be used to screen the glass.
There is also some fun with materials: walls are lined with bare plywood panels rippled with gold leaf (mixing the cheap with the precious);
balustrades are simply sheets of toughened glass (Rem seems to have declared war on the handrail); doors to boxes are dampened acoustically with gold lurex padding, and parodies of Portugal's historic blue-andwhite painted azulejo tiles line the VIP suite. A labyrinth of promenade spaces, foyers and staircases loop and wrap around the main hall and its smaller sibling that can accommodate 350 people. Below ground is a subterranean netherworld of dressing rooms and rehearsal spaces.
With its challenging non-linear geometries and unorthodox use of materials, Casa da Música certainly works hard to subvert familiar conventions, but whether it will appeal to the sensibility of a city schooled in the reticence and sobriety of Siza and Souto de Moura remains to be seen. Appropriately, Lou Reed, ageing subversive and arguably the godfather of punk, kicks off the inaugural concert season on 14 April.