Music festivals have become one of the defining cultural experiences of the modern era — temporary cities of music, community, and shared experience that attract millions of people every summer. Glastonbury in Somerset, England is widely considered the greatest music festival in the world — a five-day event of extraordinary scale and diversity that has hosted every major artist of the last 50 years in a setting of legendary mud and magic. Coachella in California has defined festival aesthetics for a generation and attracts the biggest names in pop, hip hop, and electronic music to the California desert. Tomorrowland in Belgium is the greatest electronic music festival on Earth — a theatrical spectacle of breathtaking production values. Burning Man is not a music festival in the traditional sense but a temporary city of radical self-expression that has influenced culture far beyond music. What is the greatest music festival in the world?