The original version of this multi-purpose building was designed by the New York firm of York & Sawyer. Later modifications were made under the direction of Delano and Aldrich, architects of Kykuit, and William Welles Bosworth, the noted landscape architect, who was concurrently engaged in designing and constructing the Orangerie and gardens of Kykuit. As completed in 1902, the main floor contained a carriage room and stables, but with the rapidly growing use of automobiles, provision soon had to be made to garage them. These accommodations were made by transforming the carriage room into the automobile garage and relocating the carriages to part of the stable area. Further modifications and enlargements, including the mechanic shop and clock tower were undertaken in 1913 and completed in 1915 under the direction of Bosworth. As it stands today, the three-story structure is an irregular rectangle with exterior dimensions of 145' x 110'. It was built of locally quarried rough-faced dark gray granite, random ashlar, and covers a ground area nearly three times as large as Kykuit. The clock tower with chimes is the only ornamental feature. Otherwise the ivy-covered building is impressive because of its mass rather than style and detail. Its position on a steep hillside permitted direct road access to the basement level, now meeting rooms of The Pocantico Center, but once part of the estate maintenance facilities, garage space and a boiler plant that heated both the building and Kykuit. The apartments and staff bedrooms of the top floor have been converted to guest rooms for those attending conferences.
The main level is divided into two halls which house carriages and automobiles connected by a tack room and display area. The large carriage room has to the north a comparably sized stable with seven box stalls.