New York City (NYC) or simply New York (NY), is the most populous city in the United States.Many districts and landmarks in New York City are well known, with the city having three of the world's ten most visited tourist attractions in 2013and receiving a record 62.8 million tourists in 2017. Several sources have ranked New York the most photographed city in the world. Times Square, iconic as the world's "heart" and its "Crossroads", is the brightly illuminated hub of the Broadway Theatre District, one of the world's busiest pedestrian intersections, and a major centre of the world's entertainment industry. The names of many of the city's landmarks, skyscrapers, and parks are known around the world. Manhattan's real estate market is among the most expensive in the world. New York is home to the largest ethnic Chinese population outside of Asia, with multiple signature Chinatowns developing across the city. Providing continuous 24/7 service, the New York City Subway is the largest single-operator rapid transit system worldwide, with 472 rail stations. Over 120 colleges and universities are located in New York City, including Columbia University, New York University, and Rockefeller University, which have been ranked among the top universities in the world.