A tower is a tall structure, with the diameter of its base less than its height. Rapunzel lived in a tower. If you have a super tall friend and you're short, you could say they tower over you.
Towers can come in handy––you can build one and climb to the top, looking out for approaching enemies, or in the case of a fire tower, for early signs of forest fires. One of the most famous towers is the Tower of London, with its long-held reputation as a place of torture and execution. Most people are surprised to learn that only seven people were executed in the Tower.