The selection of Yoshio Tanaguchi as the architect for the new building reflected that old MoMA distinction for quality over mediocrity. The new museum, a seamless integration of the many faces of the old MoMA within a larger whole, is beautifully elegant and understated. In a feat of egoless heroics, it is as if, rather than assert his own voice, the architect has merely cut the fat, expanded already existing space, restored former elements, and then made brilliant connections between them all.

Mr. Tanaguchi has created a new, multi-story complex with a 10-story building above it and has nearly doubled the size of the museum. His design, both inside and out, balances the best aspects of contemporary taste with the International Style, as it respects MoMA’s past architects. With a gorgeous facade of glass, aluminum, and black granite, Mr. Tanaguchi has boldly united the restored 53rd Street facade of the 1939 Goodwin and Stone building (including the original “piano” canopy), the 1964 Philip Johnson addition, and Cesar Pelli’s 1984 Museum Tower.

The museum’s new, block-long lobby, an airy, subtly ascending ramp of green slate, glass, and stainless steel, can now be entered from both 53rd and 54th Streets. The new T-shaped lobby provides a large space to gather and converse. It connects visitors to the street yet also provides an inward sense of elevated purpose. Light-filled, the lobby rises grandly into the atrium spaces and on up to the suspended walkways, and provides stunning views of, and access to, the Abby Aldrich Rockefeller Sculpture Garden, which has been restored to its larger 1953 design by Philip Johnson. The Goodwin and Stone building, through which visitors used to enter MoMA, now marks the entrance to the Modern restaurant and the renovated Roy and Niuta Titus Theaters.

Mr. Tanaguchi has provided a framework that allows for artworks in one gallery to be seen in relation to far-away works in the sculpture garden, the atrium, or other galleries. He integrates vertical and horizontal planes and spaces, carrying viewers onward in ways that are reminiscent of Frank Lloyd Wright and traditional Japanese architecture. Mr. Tanaguchi has a Miesian sense of clarity, yet the museum flows naturally. With varying ceiling heights and the appearance of sudden windows, it provides visitors with intimate spaces and grand vistas; with external views of the city and internal, vertiginous feelings of rise and fall.