When Doors Open began in 2000 as a one-time millennium event to celebrate Toronto's architectural heritage, organizers never imagined the enthusiasm with which residents would greet it.
The weather was warm, an important factor determining turnout each year, and tens of thousands streamed through the city's most distinctive buildings, making Toronto the first city in North America to recognize the interest that its architecture would generate.
"Doors Open gives people one weekend to take the pulse of the 'built city' and find out where in the city the pulse is beating faster that year," said Jane French, who developed the Doors Open program for Toronto based on a heritage program that started in Europe in the 1990s.
"When we got 70,000 people out that first year, we knew we were on to something that the public had a great pent-up interest in," said Ms. French, who is now museum administrator for the City of Toronto. "And it's just kept growing since then. Already by year five we had to start turning away some buildings because we had so many that wanted to take part."
Members of the architectural community have been supportive because of their interest in promoting the importance of good design.
Doors Open allows people to see the interiors of buildings that are usually not open to the public, said Jack Diamond, co-founder of Diamond Schmitt Architects, which has five buildings included on this year's list, including the new Li Ka Shing Knowledge Institute. The Diamond Schmitt office building is on the Doors Open 2012 tour.
"To really appreciate architecture, one must see the relationship between content and container," said Mr. Diamond. "After all, it's true for architecture as for people: True beauty is not only skin deep."
Among sites included in Doors Open most years are: the city's oldest surviving building Scadding Cabin, built in 1794 as a residence for a clerk to the first lieutenant-governor of Upper Canada, John Graves Simcoe; Union Station, the opulent Beaux-Art railway terminal opened in 1920; and the Art-Deco-style R.C. Harris Water Treatment Plant opened in 1941 and described as one of Canada's most spectacular public buildings with its marble-laden interior. (For a complete list of Doors Open 2012 sites visit: toronto.ca/doorsopen2012)
Along with those classic heritage buildings, the event has also featured some of the more recent architectural highlights including: TD Centre's impressive black Mies van der Rohe office towers; the Portlands Energy Centre; and the Canadian Broadcasting Centre's distinctive red grid exterior design and soaring atrium.
The Doors Open theme for Toronto this year is The War of 1812's Bicentennial.
But over the past 13 years, as more than two million people have gone behind the scenes at great Toronto buildings on the last week of May, important changes have taken place.
The first is that Doors Open itself has spread across Ontario, where 57 communities are hosting events this year, and it is beginning to take root in most other provinces with the exception of three, in communities from St. John's to Richmond, B.C.
In the United States a similar program called Open House, which uses a business model that supplements the Doors Open free-admission concept with a revenue-generation component that allows people to skip lineups by buying a passport, has attracted the interest of some communities.
New York organizers, who visited Toronto for advice on their weekend program that began in 2003, opted for the Open House model with the option to purchase a $150 passport that allows buyers to head for the front of the line.
Another outcome of Doors Open is that it is encouraging a public discussion about the role that architecture play in shaping the livability of a city. Some expect this debate will eventually lead to more well-designed buildings, even though they acknowledge that "condo ghettos" are also on the rise.
"It's always really hard to show cause-and-effect with this kind of thing," said Margie Zeidler, whose family has been involved in the rejuvenation of heritage buildings in Toronto such as her 401 Richmond studio building for artists and the Gladstone Hotel. "But I think the great success of Doors Open proves to the politicians, and to developers, that people do care about their heritage. They know that a city becomes a better place to live when the character of great old buildings is preserved."
This year, more than 20 of the 135 sites on the list have either been built, such as the Corus Quay building, or have undergone a major transformation, such as the MaRS Centre, since Doors Open began.
Neil Wright, head of a real estate sales company and long-time member of the Doors Open advisory committee, agrees that there are many wonderful examples of good buildings that are being built and heritage buildings that are being saved now.
"Look at the Distillery District," Mr. Wright said. "It's providing a sense of neighbourhood that's adding character to a whole new area of development in the city's downtown. Imagine what that part of town would be like if the old distillery buildings hadn't been saved. Or look at the Daniels organization (which is building mixed-use, mixed-income buildings as part of the rejuvenation) at the Regent Park housing project. Even Tridel is building green buildings now."
He acknowledged that there are still plenty of poorly designed and badly constructed buildings going up.
"But everybody's talking about heritage buildings, about architecture," Mr. Wright said. "And you know when the public gets involved like that it's going to lead to good things."
See what's behind the doors
Highlights from Doors Open events across Canada:
Toronto: Scadding Cabin (built in 1794)
The city's oldest surviving building built as a residence for a clerk to the first lieutenant-governor of Upper Canada, John Graves Simcoe. Doors Open Toronto: May 26-27.
St. John's: Anderson House (built 1804-05)
Oldest surviving building in St. John's. With a large open fireplace in the kitchen, it represents the hip or cottage roof homes popular before the fire of 1816. Doors Open St. John's: August
Dresden, Ont.: Uncle Tom's Cabin Historic Site (built 1841)
Built by Josiah Henson, a black slave who escaped the United States via the Underground Railroad and established a refuge for fugitives from slavery in this county. Doors Open Chatham-Kent: Sept. 29-30, 2012
Ottawa: The Diefenbunker (built 1959-61)
Built secretly during prime minister John Diefenbaker's leadership, the building was to serve as a government site in the event of nuclear war. It now serves as Canada's Cold War Museum. It has been voted one of Ontario's most popular Doors Open sites. Doors Open Ottawa: June 2-3.
Winnipeg: Royal Canadian Mint (built 1976)
Produces all of Canada's coins at a capacity of up to 20 million a day, the ultra-modern, pyramid-shaped facility also makes coins for more than 75 countries. Doors Open Winnipeg: May 26-27.
Edmonton: Ukrainian Cultural Heritage Village (circa 1892-1930)
Showcases the Ukrainian settlement in East Central Alberta from 1892 to 1930 with 30 historic buildings, including three churches of Eastern Byzantine Rite, a functioning grain elevator, blacksmith shop and sod hut. 2012 Historic Festival and Doors Open Edmonton: July 3-8.
Fredericton, N.B.: The Brydone Jack Observatory (built 1851)
Canada's first astronomical observatory was built as a result of the drive of University of New Brunswick mathematics professor William Brydone Jack, one of Canada's pioneer astronomers. Doors Open Fredericton: September.