If architecture is one of the things you love most about Chicago, then this is your festival. And if you believe Louis Sullivan is responsible for the best of Chicago architecture, then this is not just your festival, but your year, as the Great Chicago Places and Spaces festival celebrates the sesquicentennial (that's 150th anniversary -- maybe you knew that, but I had to look it up) of Sullivan's birth. The festival opens on Friday 19 May with a "great conversation" featuring Jaime Lerner, former mayor of Curitiba, Brazil, one of the most progressive cities in the world, and continues with two days of guided tours. Tours are free, but require tickets. Depending on the tour, you may need to line up at the Chicago Architecture Foundation on the day of your tour to get your tickets, but for "Great Excursions" (which include Chicago River cruises), you can register here starting today. Complete tour details are available here -- note that items in blue are Sullivan-centric.