Locks, fortresses, strengthenings
Castle is a type of residential and fortified structure built in Europe and the Middle East during the Middle Ages by European nobility. It is considered to be the private fortified residence of a lord or noble. At that time there were the feudal fragmentation in Europe and feudal lord's castle should had fulfilled many defensive tasks. Usually castles were built on hills, islands, rock ledges and on other places that were hard to reach. The main part of a medieval castle was a central tower - donjon that played the role of a citadel. In addition to its defensive function a castle was also a residence of a feudal lord. Often in the main tower were situated living rooms for other inhabitants of a castle, wells and other outbuildings.
In the Middle Ages on the territory of Belarus (especially in its western part) under the threat of invasion of the Teutonic Knights were built many castles and fortresses. Foreigners call Belarus - «a country of castles». You coud meet castles every 40-60 miles at that time. But unfortunately most of these unique objects were destroyed during the Livonian War, the War with Napoleon, two World wars.
Fortification is a military construction or building designed for defense in warfare and military bases. Humans have constructed defensive works for many thousands of years, in a variety of increasingly complex designs. The term is derived from the Latin fortis («strong») and facere («to make»). There are field and long-term fortifications.