text: There is a three-story shopping concourse at the base of the stilts, originally called the Market. The lowest level, corresponding to the lower lobby, includes a plant-filled atrium measuring  high, with a skylight measuring . The corner of Third Avenue and 54th Street contained an entrance to the lowest level of the shopping concourse, while on 54th Street was an entrance to the second level. The storefronts were designed to blend in with the plaza and street, with similar floor surfaces and transparent exterior walls. Overall, the stores were intended as a commitment to the city, a corporate symbol, and a tourist attraction, according to one of Citicorp's vice presidents, Arthur E. Driscoll. From 1987 to 2008, the bank presented a model train exhibition in the space each December. The shopping concourse was renamed The Shops at Citicorp Center in 1995, and it was known as the Atrium by 2016.
  Mechanical features
  In the office stories, the elevators and stairs are clustered in a central core. The building contains 20 double-deck elevators,  which Otis Worldwide constructed for $7 million. Although each of the upper or lower decks serves only odd or even floors, visitors can travel between odd and even floors using escalators. Each of the elevators consists of two standard elevator cabs that operate simultaneously in one shaft. The elevators cost 25 percent more than standard elevators but allowed for a 24 percent reduction in the floor area taken up by elevators, as twenty-six single-deck elevator shafts would have been required otherwise. The Citigroup Center's double-deck elevators were likely the first to be installed in New York City since 1932, when the Cities Service Building was completed. In total, the Citigroup Center has 38 elevators.
  At Citicorp Center's completion, a "supermail" system delivered each tenant's mail. Incoming mail was sorted in the basement and transferred via lifts to each floor, where the mail was transported manually to fixed bins. The building also contained 2,500 sensors to monitor the mechanical systems, such as HVAC, lighting, electrical, sprinkler, life-safety, security, and elevator systems. The sloped roof houses mechanical equipment.