A guard tower is a structure which is designed to command an excellent view of the surrounding area. Guard towers make regions more defensible by giving people an opportunity to see potential threats from a great distance, and they are also used as a form of crowd control, since guard towers can be used to keep an eye on citizens. Typically, guard towers are significantly higher than the surrounding structures and geographical features, to keep the view free and unobscured.
The practice of building guard towers is ancient. Numerous archaeological sites in former cities and urban areas show evidence of guard towers at high points in the surrounding area, and guard towers on castles and similar structures have endured to this day. Such towers are also an important part of modern prison architecture, and they are also used by many militaries along contested borders and at military facilities which require protection.
As the name implies, a guard tower is usually a tower, rather than a more extensive building, and guard towers are designed for utility, not comfort. The space inside is often cramped, and used to store things like weapons, surveillance equipment, and other supplies which may be necessary. If the possibility of a siege is suspected, the guard tower may also be stocked with food, drink, medicine, and so forth, to ensure that the guards can hold their ground. Modern guard towers usually have extensive communications equipment as well.
People posted in a guard tower usually have some sort of military training. When a guard tower is used to defend an area from an exterior threat, the workers in the tower are usually authorized to send out warning shots and to use a megaphone to order people away. Guard towers may also be used to keep an eye on gates and entrances, so that gatekeepers have backup if a problematic situation emerges.
When a guard tower is used to keep people in a location such as a prison, the guards are often more focused on the activities inside the perimeter, although they also keep an eye on the outside for signs that someone might be trying to assist people on the inside. Prison guards typically increase their numbers during yard exercise, prison transfers, and other situations where prisoners might escape, and they are usually equipped with tools to stop people from going over the fence.
The guard tower is often used as a symbol of totalitarian regimes, because such towers can become a daily part of life for people living under such regimes. Aside from the towers erected at prison camps and military installations, guard towers may also be used to monitor and control the citizens. Guard towers along the Berlin Wall, for example, were used to keep East Germans from defecting to the West.