People watching is at its best in London’s Trafalgar Square. With site festivals, the occasional protest, and almost always lots of tourists, the large plaza is a great place to sit in and stare. Just climb up onto the central monument with a cup of tea or coffee and watch the people go by. Afterward, head to the National Gallery, the crowning glory of the square as the home of hundreds of the most famous and most beautiful paintings in the world. This vast space features Western European paintings from the 13th to 19th centuries, including works by masters like Van Gogh, da Vinci, Picasso, Michelangelo, Botticelli, Renoir, and Titan. As it’s free to visit, if you’re limited on time and want to see just one great masterpiece, view Holbein’s “The Ambassadors.” Laden with symbolism, it features the “anamorphic perspective” which was a technique popular in Early Renaissance art. The seemingly smudged image in the foreground is transformed into a human skull when viewed sideways.