Copenhagen’s Opera House is hard to miss. The immense building measures some 440,000 square feet and presides over the harbor from its position on the island of Holmen, across the water from the palace at Amalienborg. Completed in 2004, it was designed by Danish architect Henning Larsen, and thanks to a generous benefactor, no expense was spared: Jura limestone, Italian marble, even oak from a grove of 19th-century trees are just a few of the materials used, and the walls are lined with works by contemporary Danish artists. (Final construction costs totaled more than $500 million, making it is the most expensive opera house ever built.) Fortunately, tickets to the main stage and the experimental Takkelloftet theatre are not always limited to the very rich. Occasional last-minute bargains are available, especially if you sit in the nosebleed section, and state-of-the-art acoustics ensure that the sound there is every bit as good as it is on the main floor.