Doors Open Toronto is an annual event when approximately 150 buildings of architectural, historic, cultural, and social significance to the city of Toronto open their doors to the public for this free citywide event. Doors Open Toronto was developed as a millennium project in 2000, by the City of Toronto (developed from a European model) and has since attracted over 1.7 million residents and tourists. Doors Open Toronto gives people of all ages and backgrounds the opportunity to learn about Toronto's history, get involved and celebrate Toronto's built heritage.