Key Insights:

• The Scale King: While the Louvre is the world's most visited museum, its status as a historical complex often complicates 'single-building' metrics.
• Modern Expansion: New facilities like the Grand Egyptian Museum leverage modern architecture to create massive, unified exhibition volumes.
• Defining Challenges: Large institutions like the Metropolitan Museum of Art often achieve massive square footage through complex underground expansions, blurring the lines of 'single-building' architecture.