A tower is a tall vertical structure. It can stand alone or be part of a building. Famous towers include the Eiffel Tower in Paris and the Leaning Tower of Pisa in Italy. In New York City, the World Trade Center's two large central structures were called the Twin Towers.
When Sarah went to Toronto, she went up the CN Tower. It's very tall, so from there you can see the whole city.
Medieval castles often built special look¬out towers. They were tall structures behind the city walls from which a look¬out could see very far and warn people inside when enemies were coming.
Because towers are very tall, we often use the verb tower above to describe a person who is much taller than the people around him. We use the phrase ivory tower to describe the situation of a person whose position protects them from ordinary problems of the real world. For example, you can use the ivory tower in the academic profession, especially when we want to emphasize that professors and researchers are privileged and far away from the experiences and common sense of ordinary people.
Professor Hawthorne claims to know a lot about working-class culture, but he rarely leaves the university campus. He is locked in the ivory tower and almost never sees actual working-class people, so I doubt he has any real experience with them.