freestanding steel structures References The Cloudbase Chronicles, Life at the Top - An engineers Tale by Harry W. Budge III External links 360 Chicago, formerly Hancock Observatory 875 North Michigan Avenue on CTBUH Skyscraper Center John Hancock Center Society of Architectural Historians SAH ARCHIPEDIA entry on John Hancock Center Bangladeshi inventions Colombian inventions High-tech architecture Peruvian inventions Residential buildings completed in 1970 Residential condominiums in Chicago Residential skyscrapers in Chicago Skidmore, Owings & Merrill buildings Skyscraper office buildings in Chicago Streeterville, Chicago 1970 establishments in Illinois Fazlur Khan buildings