I just found out about the sudden death of Bob Cassilly, founder of the City Museum in St. Louis. This is the saddest of news for St. Louis, and for museums everywhere.Cassilly's City Museum is not your traditional city museum; it's not really a traditional museum of any kind. But it should be an inspiration to all of us, nonetheless. It is a place for full-blown imagination and play, with caves, multi-story slides, a roof-top ferris wheel, boxing robots, a Wurlitzer pipe organ, all made from found objects. It's a place "where people can come and do things they’re not supposed to,” according to Cassilly. It's a children's museum on steroids. Or what a theme park looks like when it's designed by an artist instead of by Disney.Cassilly and the museum attracted a fair amount of controversy over the years, but the most interesting projects usually do. If the city museums I work with and study, the traditional city museums, could harness just 10% of the sense of wonder Cassilly produced at his City Museum, they could create a much more engaging visitor experience. So all of you city museums out there, in honor of Bob Cassilly, today is the day to do something creative. Put an artist on your board of directors. Tell visitors a joke about your city when they check in at the front desk. Figure out what urban history tastes and smells like. Think about what it would mean to create a museum that's like no other place on the planet. Let's make him proud.