This 1911 masterpiece of beaux-arts design (Carrère and Hastings, architects) is one of the great research institutions in the world, with 6 million books, 12 million manuscripts, and 2.8 million pictures. But you don't have to crack a book to make it worth visiting: both inside and out, this stunning building, a National Historic Landmark, will take your breath away with its opulence.

Originally financed in large part by a bequest from New York governor Samuel J. Tilden, the library combined the resources of two 19th-century libraries: the Lenox Library and the Astor Library. The latter, founded by John Jacob Astor, was housed in a building downtown that has since been turned into the Joseph Papp Public Theater. Today the library anchors a network of close to 200 local branches throughout the city. You can see unusual behind-the-scenes collections, ranging from 19th- and early-20th-century menus to the personal library of magician Harry Houdini.

The grand entrance is at 5th Avenue just south of 42nd Street, where a pair of marble lions guard a flagstone plaza. Mayor Fiorello La Guardia, who said he visited the facility to "read between the lions," dubbed them "Patience" and "Fortitude." Statues and inscriptions cover the white-marble neoclassical facade; in good weather the block-long grand marble staircase is a perfect spot to people-watch.

The library's bronze front doors open into the magnificent marble Astor Hall, flanked by a sweeping double staircase. Upstairs on the third floor, the magisterial Rose Main Reading Room -- 297 feet long (almost two full north-south city blocks), 78 feet wide, and just over 51 feet high -- is one of the world's grandest library interiors. It has original chandeliers, oak tables, and bronze reading lamps that gleam as if they were new. Gaze up at the ceiling and you can see murals of blue sky and puffy clouds, inspired by Tiepolo and Tintoretto. Exhibitions on photography, typography, literature, bookmaking, and maps are held regularly in the Gottesman Exhibition Hall, the Edna B. Salomon Room, the Third Floor Galleries, and the Berg Exhibition Room. Free one-hour tours leave Tuesday-Saturday at 11 and 2 from Astor Hall. COST: free. Subway: B, D, F, V to 42nd St.