Rising up on the Rockefeller Plaza's west side is the 70-story (850-foot-tall) art deco GE Building, a testament to modern urban development. Here, Rockefeller commissioned and then destroyed a mural by Diego Rivera upon learning it featured the Communist leader Vladimir Lenin. He replaced it with the monumental American Progress by José María Sert, still on view in the lobby, flanked by additional murals by Sert and English artist Frank Brangwyn. While in the lobby, pick up a free "Rockefeller Center Visitor's Guide" at the information desk (212/332-6868). Sixty-five floors up, the glittering Rainbow Room (opened in 1934) brings the Rockefeller era to life with dancing and big-band music. The GE Building also houses NBC Studios (212/664-7174), whose news tapings, visible at street level, attract gawking crowds. For ticket information for NBC shows or the 70-minute studio tour, visit the NBC Experience Store at the building's southeast corner. 30 Rockefeller Plaza, between 5th and 6th Aves. at 49th St., Midtown West. NBC Studio Tour $18.50. Children under 6 not permitted. Tours depart every 30 mins Mon.-Sat. 8:30-5:30, Sun. 9:30-4:30. Subway: B, D, F, V to 47th-50th Sts./Rockefeller Center.