Tourism is the most important source of income in Hawaii. Honolulu and other communities have developed a sophisticated travel industry to care for visitors. Honolulu ranks first in tourist arrivals. Some of the state's most visited attractions are within its boundaries. In Oahu, most of the tourism activity is centered in the Waikiki district of Honolulu. With more than 30,000 hotel rooms, luxury resorts, expensive international restaurants and shops, and beautiful beaches, Waikiki attracts hundreds of thousands of visitors each year.
In Honolulu, and nearby, the most visited sites have military connections. The USS Arizona Memorial and Visitors Center in Pearl Harbor ranks first among visitors, while Punchbowl Crater, home of the National Memorial Cemetery and final resting place for 34,000 veterans of World War II and the Korean (1950–53) and Vietnam (1945–1973) wars, is a close second. The retired battleship USS Missouri was brought to Pearl Harbor in 1998 and has become a major visitor attraction. The Queen Emma Summer Palace also is a favorite destination. Iolani Palace, the only royal palace in the United States, was built in 1882. It is located in downtown Honolulu.