A month before Hitler invaded Poland in 1939, Mahatma Gandhi wrote him a letter imploring him to “prevent a war which may reduce humanity to the savage state”. That letter, which began with “Dear friend” and which Hitler, as we all know, did not heed, is now floating in fog. Literally. Artist Jitish Kallat has projected the letter onto fog to create an immersive video installation called Covering Letter (2012) that allows visitors to step into that moment in history just before World War II. The artwork is on display at La Biennale di Venezia, or simply the Venice Biennale