The Great Festival presents and analyzes two historical festivals - the ancient Dionysus Festival and the present Roskilde Festival. The purpose is to set up two comparable structures or 'codes' to explain the universal artistic effects, structures and fascination of the festival. Olav Harsløf argues that there are major structural, organizational and economic similarities which, when exposed, can give us greater insight into today's festivals. This is illuminated through a combined performance design and event analysis of the ancient Dionysus festival and today's Roskilde Festival, explaining the festival's historicity, diversity, complexity and paradigmatic strength. This will be a discussion of great interest to researchers and students in the fields of performance studies, experience economy, theater, music, classical philology and archeology.