Croatia's entertainment culture uses its geography cleverly. The Midsummer Scene festival stages performances in the Roman arena at Pula — an amphitheatre that has been hosting events since 23 AD, making it one of the world's longest continuously used entertainment venues. The Dubrovnik Summer Festival brings theatre, dance, and music to the city walls, open-air stages, and courtyards of a UNESCO World Heritage city in July and August. The Ultra Europe electronic music festival in Split, held in stages around the Dalmatian coast, is one of Europe's largest and most geographically dramatic music events. The klapa a cappella singing tradition of Dalmatia — a UNESCO-listed male vocal harmony form — provides the specifically Croatian entertainment register that the nightclub circuit does not.