The issue of elevators was a major limiting factor in building height. The taller the building, the more elevator needed to service the building and that means consuming more space for the elevators. Yamasaki and the engineers decided to introduce a new system of sky lobby, floors where people could switch from large – capacity express elevator which serves the sky lobbies, to a local elevator that goes to floors in sections.
The sky lobbies were located on the 44th and 78th floor of each tower that increased the amount of usable space on each floor about 75 percent. Altogether, the twin towers had 95 express and local elevators. This system was inspired by the subway system of New York.
Yamasaki’s design for the Twin Towers was announced to public on 1964. The buildings were designed with narrow office windows 18 inches wide each that showed that he tried to make the occupant feel safe in building. Yamasaki’s design also included Aluminum – Alloy facades.
In addition to the Twin Towers the design included four other low – rise buildings which were built in 1970. The design of the Twin Towers was not easy to decide but by the hard work of Yamasaki this dream came true and this huge building occupied a place of 16 acres on the whole.

The twin towers, both the North and the south were each roughly 1360 ft high, 1960 ft long on each side. Each of them had 110 floors and had 104 elevators and rested on foundations that were 69 ft into the bedrock and was a city in itself. Their construction required 200,000 tons of steel to give it flexibility so that it can endure heavy storms without breaking into pieces and 3000 miles of electrical cables to satisfy the distribution and consumption of about 80,000 KW per day. The structures were divided into three vertical zones for express elevator ascent. If we talk about the ventilation the towers design was made so to make it properly ventilated by placing 43000 windows, each 22 inch wide. And instead of walls or card boards, glass was heavily used in the structure, in total the facades required 215000 sq. ft of glass.

But before all this construction there was a need for 12,000,000 sq. ft land for the building in New York City which was not at all an easy task. The Designer Yamasaki provided 100 models for world trade centre before the two towers were selected, which presented a breakthrough configuration compromise. In the creation of Twin towers Yamasaki had to go beyond the traditional ways of construction and had to think of new ideas as this was not a simple project as other projects. This was the world’s largest project and he completed it successfully.