Complex sentence: Windows on the World was an elegant restaurant and adjoining bar that operated between 1976 and September 11,2001 in New York City on top floors (106 and 107) of the North Tower of the World Trade Center.
Split into simpler sentences: Windows on the World was an elegant restaurant and adjoined bar that opened in 1976. It was located in New York City on top floors (106 and 107) of the North Tower of the World Trade Center.