Towers are tall structures that are primarily constructed towards the air. While there have been towers for industrial or civilian purposes, they also found great utility in defensive measures and fortifications.
Watch towers have existed since early ages that could overlook swathes of areas and provided scouts an easier means of obtaining information about incoming threats, such as an army marching in formation. Most of the time, watchtowers were also serving as beacons, having lit up flames high enough on their top to emit light visible in big distances. While their utility was immeasureable, they were easy to demolish and remove by tools and weapons.Fortified towers made of stone appeared early in castles of the Medieval Ages. These towers were built on a stable foundation so that they could easily shrug off catapulted rocks, as well as they were able to host groups of defenders on the top and in the medium levels. Towers were later provided additional features that made retaliation possibilities better and safer: arrowslits, holes for pouring out hot liquids and stakes. Grand towers were able to house heavy mechanical equipment such as mangonels and springalds (later cannons).
In sieges, towers were a crucial weak point of a castle and the attacking force often deployed siege equipment - mechanical devices that used heavy projectiles to damage the structure of a tower and crumble it. Rocks and iron balls were really effective in this, but very unreliable due to their long arming time and preparations. Sometimes, a more brute but stronger and heavier battering ram was used for the task.
Castle towers remained well in use until the 17-18th century, even in the era of cannonballs and gunpowder.