The gilded opulence of a Buenos Aires ballroom, the hidden tunnels beneath Jerusalem’s Wailing Wall, and the cavernous innards of the biggest gasometers in Europe are some of the off-limits sites that can be glimpsed around the world this autumn, thanks to the growing phenomenon of the Open House weekend.  The initiative, which began in London in 1992 and celebrates its 22nd edition this week, has since spawned a global network of over 20 cities, from Barcelona to Brisbane, Tel Aviv to Thessaloniki, joined in the last couple years by Gdynia in Poland and the Cypriot capital of Nicosia. The combined programme now includes thousands of buildings and locations, from the lavish halls of embassies and parliaments, to the industrial heft of cement factories and sewage treatment plants, as well as micro-flats and self-build housing schemes, with the number of participating cities expanding year upon year.  “They’re like feral cats, they just keep on arriving,” says Victoria Thornton, who founded the initiative as a “mad idea” to get people more interested in their surroundings, beginning by knocking on doors and pestering building owners herself. The London weekend has since ballooned into a city-wide festival of more than 800 locations, manned by an enthusiastic army of 2,000 volunteers.  This year, the old crowd-drawing favourites of the Foreign Office, Bank of England and Gherkin are joined by the Cheesegrater tower by Rogers Stirk Harbour and Partners. Each are expected to attract over 5,000 visitors, lured by the thrill of waltzing past security barriers and peering behind locked doors.  For architectural anoraks, the international programme offers new excuses for far-flung pilgrimages, including some rarely opened buildings by Mies van der Rohe and Frank Lloyd Wright in Chicago and an Alvar Aalto-themed jog across Helsinki – a 10km route for design disciples that ended up with a rewarding steam in the Finnish maestro’s home sauna.  Vienna staged a particularly diverse line-up, including a trio of gargantuan 1940s grain stores shaped like scaled-up houses and stuffed with a tangled network of pipes and chutes, along with a luxurious apartment designed by Adolf Loos in 1913, now home to a popular pensioners’ bridge club. The socialist slab of the Karl-Marx-Hof tenement complex also opened its doors, alongside more recent Baugruppen co-housing schemes. “In Austria we are very nosey,” says organiser Iris Kaltenegger. “We really like to see how our neighbours live.”  Rome’s weekend, which was held in May, offered a rare glimpse inside the imposing Palazzo della Civiltà Romana, a cubic Colosseum of sparkling white arches in the fascist satellite city of EUR, as well as a group of majestic 1930s gasometers in Testaccio. New York’s annual highlight, meanwhile, is Eero Saarinen’s defunct TWA Terminal at JFK airport, a long abandoned 1960s concrete hymn to the drama of flight, which its owners are threatening to turn into a hotel.  It’s the discussion of such issues that Open House aims to bring to the fore. “It’s not supposed to be aimed at tourists or cultural promotion,” says Thornton. The event must be run by an independent organisation in each city, and not be affiliated to municipal departments or tourist boards. “It’s about getting residents back out on their streets and looking at their own city. It should prompt these conversations and make people start demanding something better.”  It is a politicised call to arms taken up by some of the more divided cities to stage the event, including Jerusalem and Nicosia. Aviva Levinson founded Houses From Within, the Israeli version of Open House, in 2007, with her architect husband, Alon Bin Nun. “We see it as a great model for encouraging a debate about the city in a secular, civilian way of thinking, against the volume of religious extremism here,” she says. The programme ranges from Moshe Safdie-designed housing in the Jewish quarter to Palestinian sites in the east of the capital.  In Nicosia, which held its first Open House weekend in May last year, the event treads carefully between the desires of both Greek and Turkish Cypriots. “We try to promote the reunion of the two communities,” says co-ordinator Andreas Kourouklaris, “by opening up the historic buildings that were constructed when Nicosia was one, and the people lived in harmony.” Enrapt in the ethereal light of the 14th-century Hamam Omerye or the Saint John chapel, it might be easy to find a momentary salve for contemporary political turmoil.  Next year will see the event extended to Prague and Cork, Belfast and Monterrey. The organiser of the latter, Daniel Fernández, was inspired by visiting the event in Barcelona while studying there. “I thought it was a great idea, not just for locals to visit their city’s buildings,” he says, “but as a tool to show real estate developers, politicians, business people and citizens what architecture is – and why we should protect those architectural gems that we have.”
From London to Brisbane to Buenos Aires, architecture enthusiasts all over the globe get set to nose around in the world’s greatest buildings for free, writes Oliver Wainwright