Many of our articles discussing tall buildings refer to 'sky lobbies.' In the context of tall buildings, a sky lobby serves as an intermediary level where passengers transfer between non-connected banks of elevators. Ever increasing building heights in the mid-20th century have created a need for better elevator efficiency, which was first addressed in Chicago's 1969-built John Hancock Center.
To efficiently serve the upper floors of the 100-storey, 344-metre tower, a 'lobby' was built on the 44th floor which serves only the tower's residential levels from 45 to 92. Residents of the tower's upper levels use express elevators to bypass the first 43 levels and travel directly to the sky lobby, before boarding 'local' elevators to reach their destination floors.
The sky lobby has become much more prevalent in subsequent years, with the first towers containing multiple sky lobbies — the original World Trade Center towers — constructed in New York in 1972 and 1973, with each tower featuring sky lobbies on the 44th and 78th floors. Sky lobbies are now familiar features in skyscrapers around the world, and can be found in each of the top three tallest buildings.
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