Rockefeller Center is a large complex consisting of 19 commercial buildings covering 22 acres (89,000 m2) between 48th and 51st Streets, facing Fifth Avenue, in New York City. Commissioned by the Rockefeller family, it is located in the center of Midtown Manhattan. The 14 original Art Deco buildings span the area between Fifth and Sixth Avenues, split by a large sunken square and a private street called Rockefeller Plaza. Five International Style buildings, built later, are located on the west side of Sixth Avenue and at the head of Rockefeller Plaza. In 1928, the site's then-owner, Columbia University, leased the land to John D. Rockefeller Jr., who was the main person behind the complex's construction. Originally envisioned as the site for a new Metropolitan Opera building, the current Rockefeller Center came about after the Met could not afford to move to the proposed new building. Various plans were discussed before the current one was approved in 1932. Construction of Rockefeller Center started in 1931, and the first buildings opened in 1933. The core of the complex was completed by 1939. Rockefeller Center has two parts: the original center and the later International-style buildings. The original center has several sections: Radio City, for RCA's radio-related enterprises such as the Music Hall and 30 Rockefeller Plaza; the International Complex, for foreign tenants; and the remainder of the original complex, which originally hosted printed media as well as Eastern Air Lines. While 600 Fifth Avenue is located at the southeast corner of the complex and contains architecture similar to the original complex, it was built by private interests in the 1950s and was only acquired by the center in 1963. Described as one of the greatest projects of the Great Depression era, Rockefeller Center was declared a New York City landmark in 1985 and a National Historic Landmark in 1987. It is noted for the large quantities of art present on almost all of its Art Deco buildings, as well as its Radio City section and its ice-skating rink. The complex is also famous for its annual lighting of the Rockefeller Center Christmas Tree.