The floor of the Smithsonian Institution Arts and Industries Building (AIB) Rotunda is made of encaustic tile; it is a replica of the 1881 historic floor, which was removed in 1957. The Rotunda floor contains a mixture of octagonal, hexagonal and square-shaped tiles of varying colors, as well as decorative floral motifs around the fountain. The only other areas in the building with encaustic tile are the floors at the exterior vestibules at the west and south entrances, which are also replicas of the 1881 floors.
The floors in the main halls are covered in marble and limestone in a decorative multicolored pattern, surrounded by a dark slate edge and a tinted concrete border. The decorative pattern consists of square black-and-white patterns across the width of the halls, with of black and red stone separating the squares in both directions. This flooring dates to 1881, when it replaced the original wood flooring that was installed for Washington, D.C. Inaugural Ball of President Garfield. A number of fossils can be found in the black marble as the sedentary composition that formed the marble was once under sea water and trapped small marine life.
The terrazzo flooring in the galleries is a mixture of original construction dating from 1898 and replacement of the previous wood board finish. Likewise, any original wood in the first floor courts has been replaced by terrazzo; concrete, vinyl and carpet cover other areas of the courts as well.
The original wood floor in the ranges has not survived. Much of it was replaced by terrazzo in the early 20th century, though this too has been replaced or covered over by carpet, pattern vinyl composition tiles, and ceramic tiles. Most of the floors in the pavilions and towers are now carpeted; the floors at the basement level are concrete or are finished with vinyl composition tile.