Willis tower

So i picked  the sears tower or now called the Willis tower. So some stuff i know about the building was it was built in August 1970 the building was finished in 1973 it use to be the tallest. Building in the world. but now its not the tallest building right now. But the burj khalifa is the tallest tower but were not talking about that so the Willis tower has 110 floors and 16.100 windows and the Willis tower costed 150 million that’s all that I know. So i picked the Willis tower because it was one of the biggest building and its in Chicago city and because it costed 150 million for a building.