As summer winds down and the air turns crisp, the cultural world comes alive. From beloved annual fairs to dazzling new exhibitions, the fall offers countless reasons to plan an arts- or design-focused getaway. Here, our network of Indagare Insiders share the highlights they are most looking forward to this season, in some of our members' favorite cities—from art openings in London and landmark retrospectives in Paris to museum and theater debuts in New York and Renaissance masterpieces brought ...