One feat of engineering that is still a popular centerpiece are the medieval castles that were built throughout the middle ages. In medieval times, there were many wars and battles that were waged between different clans, nobles, and countries which led to the need for a stronghold. These medieval castles and strongholds came in the form of castles because of their ability to keep out unwanted invaders while also allowing enough space to house a small town to outlast the attacks on the outside.
Some common features of medieval castles are things like mottes and moats that added to their impenetrability. Many medieval castles featured gigantic walls to keep out the advancing hordes and to offer protection from scaling. These walls were generally very thick (around ten feet) and very tall (about forty feet). Additionally, battlements were arranged on the outside of the wall to help deflect and defend against the advancing troops. Most of these contained a combination of features that allowed soldiers to drop things on the troops below, shoot at them with arrows and defend with swords should someone breech the wall without the fear of falling.
Today, these medieval castles aren’t much use, but they did the lay the foundation for what we would need to defend ourselves against the advancing military weapons. There are many features that would look common in modern materials and that would feel like home to modern soldiers. In most castles, there may still be tenants who live there, but most have been converted to museums of some sort to allow people to better understand their purpose and to see, touch, and even smell something so magnificent to stand up to centuries of abuse.