The Manhattan Project - 1942 - Because the mission to create the atomic bomb was top secret, General Leslie Groves decided to follow the tradition of Corps of Engineers projects for the city in which they were located.  The Manhattan Project was the U.S.-led effort during WWII to develop nuclear weapons, involving the U.K. and Canada. Directed by Major General Leslie Groves, with physicist J. Robert Oppenheimer leading the Los Alamos Laboratory, the project created two atomic bombs, "Little Boy" (uranium-235) and "Fat Man" (plutonium). It employed 130,000 people and cost $2 billion (equivalent to $27 billion today).

Los Alamos National Laboratory - 1943 - Founded as the secret Project Y laboratory of the Manhattan Project, Los Alamos National Laboratory (LANL) was the primary site where scientists designed and assembled the world's first atomic bombs. Located in remote northern New Mexico, the laboratory brought together many of the twentieth century's leading physicists, including numerous Nobel laureates, and played a pivotal role in the development of the Trinity test and the bombs dropped on Hiroshima and Nagasaki. Today, LANL remains one of the world's foremost research institutions, conducting cutting-edge work in national security, supercomputing, space exploration, nuclear science, energy, and medicine.

Woolworth Building - 1913 - F. W. Woolworth, an entrepreneur who had become successful because of his "Five-and-Dimes" (5- and 10-cent stores), began planning a new headquarters for the F. W. Woolworth Company in 1910. It was the tallest building in the world when it was completed at 792'. The title lasted 21 years. The skyscraper was unusual because it was financed entirely in cash. The highlight of the opening ceremony featured United States President Woodrow Wilson throwing a switch to illuminate the building. Much of the original terra-cotta cladding has since been replaced with cast stone.The lobby is one of the most impressive in the city. It features a shining mosaic barrel vault, stained-glass skylight, marble walls, bronze fixtures, mezzanine murals entitled Labor and Commerce, and carved gargoyle representations of Gilbert, Woolworth, and other figures key to the design, engineering and construction of this landmark.

Columbia University - 1754 - The original McKim, Mead and White plan for this leading university was never completed, and buildings by contemporary starchitects have popped up over the years, giving Columbia's campus and eclectic look. Of the Classically-styled Charles McKim buildings, the monumental (if now misnamed) Low Memorial Library impresses most with its elegant steps (popular with sunbathers) and enormous dome. (Today it houses administrative offices rather than books.) Other notable campus buildings by Gwathmey Siegel, Rafael Moneo, Gruzen Samton, and Bernard Tschumi.