Toronto offers once a year the opportunity to enter a large number of sites and buildings in Doors Open Toronto. This time it was the weekend of May 25th-26th. The sheer number of buildings listed is overwhelming. But there was one I had in focus, because I caught myself already a few times pressing my nose to the windows of the R.C. Harris Water Treatment Plant at the end of our beach at Lake Ontario. It is a wonderful complex consisting mainly of two buildings: the pumping station and the filter building. Its grand 1930s architecture and Art Deco elements, made people dub it “The Palace of Purification”. There are three recommended readings which are John Bentley Mays (1992): A Masterwork of Art Deco and in the Market gallery of the City of Toronto Archives (1982), The Architecture of Public Works: R.C. Harris, Comissioner, 1912-1945. I could not find them online. But that’s just one more reason to also explore the Central Library of Toronto soon. Toronto’s 3 million people have an annual drinking water demand of 400 billion liters, and the R.C. Harris plant provides about 1/3 of it. Tap water is actually chlorinated in Toronto, which made me buy a domestic water filter to run it through first. But I can imagine, that given the over 6000 km of piping in town, chlorination is necessary to keep it safe until reaching the last corner.