The stories above the 10th floor have been converted into 157 luxury condominium units. There is a separate lobby for residents on the Barclay Street side, which connects to the original lobby. The penthouse apartment, a duplex unit on the 31st and 32nd floors, covers with a living room, advertised as the largest in the city. The building also contains an wading pool and a lap pool. Other features of the residential portion of the Verizon Building include rooms for wine-tasting and billiards; music practice; a fitness center; a children's playroom; and a residents' lounge. The Verizon Building has five sub-basement levels, which house communications equipment. At the time of the September 11 attacks, Verizon was using the building as a main telecommunications switching center in Lower Manhattan, handling approximately 200,000 phone lines and 3.6 million data circuits. These circuits traveled as far north as 42nd Street. In emergencies, the 17th floor could provide services to the building's base. The New York Telephone Company began to grow rapidly after World War I. An internal review of the organizational structure found that its New York City operations were housed in multiple buildings across the city, and were thus inefficient. The company's president from 1919 to 1924, Howard Ford Thurber, sought to centralize the company's operations into a single large headquarters to "satisfy the present demands and to reasonably anticipate future requirements". In the early 1920s, the New York Telephone Company started acquiring the entire block between West, Barclay, Washington, and Vesey Streets. The site was chosen "because real estate values in that vicinity were much lower" compared to the area around Broadway. The company owned the entire block by 1923, by which it had spent $1.5 million on acquisitions. In April 1923, the company announced that it intended to build a new headquarters at a projected cost of $11.5 million. The structure was to house 6,000 employees from the company's six central offices, who would work with 120,000 telephones, as well as mechanical equipment to support the company's equipment. The initial design called for a height of , with of office space, and of commercial ground-floor storefronts. In addition, the building would be erected with a steel-and-concrete frame, as well as facade trim made of limestone and buff-colored brick. The building was to be designed by Ralph Walker of Kenzie, Voorhees & Gmelin, who wanted to create a "strong corporate image" for the structure.