Oahu is Hawaii's most-populated and most-visited island, as well as home to the world-famous city of Honolulu and Waikiki Beach. Visitors of all ages and walks of life can enjoy a multitude of attractions and activities on the island, from dolphin swimming to historic sites. Two of the most-frequented places on Oahu are Pearl Harbor and the USS Arizona Memorial, which commemorates the attack on the base in 1941. In downtown Honolulu, visitors may tour Iolani Palace, the only palace in the United States that was inhabited by royalty. Also found in Honolulu is Chinatown, which spans 15 blocks and contains historical and cultural finds, galleries, restaurants and specialty shops. Surfer's paradise is found on Oahu's North Shore, with many surfing instructors on hand to teach beginners the ropes. Whale watching, boat touring, scuba diving and deep sea fishing are other popular Oahu pastimes.