Fortifications are structures built to protect a city or area from attack. Bastions are large, fortified towers that project out from the walls of a fortification. DEFENCES are structures built to protect a city or area from attack. Redans are triangular fortifications that project out from the walls of a fortification. Defenses are structures built to protect a city or area from attack. Ramparts are walls built around a city or fortification for protection. All of these terms refer to fortifications, which are structures built to protect a city or area from attack.