Which Chicago building was it?

I've got a stupid question, but I figured that this was the best forum to get the answer: About 10 years ago, I was in Chicago for a few days and the people I was meeting with took me to the observation floor of some pretty big tower (60, 70, 80 floors... I don't remember). From that observation floor, they pointed out the Sears Tower to me, and in my memories, it seems like the Sears Tower was right across the street from the building I was in, but I may misremember that part. Either way, the Sears Tower was very near and very visible. But I don't remember which building I was in. Any Chicagoans to help me which building I was likely to be in?>