Whether you "need" an itinerary depends on your travel style, but in 2026, a flexible framework is highly recommended for most major destinations. While "winging it" offers spontaneity, popular sights now almost universally require timed-entry reservations made weeks or months in advance. An itinerary acts as a safety net that prevents you from missing out on "must-see" attractions like the Louvre or the Tokyo Skytree, which often sell out. However, the best itineraries leave "white space" for local discovery. A well-balanced plan ensures you hit your high-priority targets while maintaining the freedom to spend a rainy afternoon in a hidden café or change your mind about a day trip. Essentially, you don't need a minute-by-minute schedule, but you do need a strategic "to-do" list with confirmed bookings for the most popular spots to ensure your trip is efficient and stress-free.