Doors Open Toronto is a yearly event featuring more than 150 significant Toronto buildings, open for free tours -- and it's happening this weekend, on Saturday, May 25 and Sunday, May 26. It's generally a very popular event and the buildings featured this year include the Art Gallery of York University, Gladstone Hotel, King Edward Hotel, Old City Hall, Steam Whistle Brewery, Archives of Ontario as well as dozens of houses of worship. There are also some new walking tours visiting several points of interest.
If you're interested in taking part in this event, keep in mind that each building has its own hours and some are offering access on one day only. There's a full of buildings with hours here.