FortificationA fortification is a military construction designed for the defense of territories in warfare, and is used to establish rule in a region during peacetime. The term is derived from Latin fortis ("strong") and facere ("to make"). From very early history to modern times, defensive walls have often been necessary for cities to survive in an ever-changing world of invasion and conquest. Some settlements in the Indus Valley Civilization were the first small cities to be fortified.
WallA wall is a structure and a surface that defines an area; carries a load; provides security, shelter, or soundproofing; or, is decorative. There are many kinds of walls, including: Walls in buildings that form a fundamental part of the superstructure or separate interior rooms, sometimes for fire safety Glass walls (a wall in which the primary structure is made of glass; does not include openings within walls that have glass coverings: these are windows) Border barriers between countries Brick walls Defensive walls in fortifications Permanent, solid fences Retaining walls, which hold back dirt, stone, water, or noise sound Stone walls Walls that protect from oceans (seawalls) or rivers (levees) The term wall comes from Latin vallum meaning ".
CastleA castle is a type of fortified structure built during the Middle Ages predominantly by the nobility or royalty and by military orders. Scholars usually consider a castle to be the private fortified residence of a lord or noble. This is distinct from a mansion, palace and villa, whose main purpose was exclusively for pleasance and are not primarily fortresses but may be fortified. Use of the term has varied over time and, sometimes, has also been applied to structures such as hill forts and 19th- and 20th-century homes built to resemble castles.
City-stateA city-state is an independent sovereign city which serves as the center of political, economic, and cultural life over its contiguous territory. They have existed in many parts of the world since the dawn of history, including ancient poleis such as Athens, Sparta, Carthage and Rome, and the Italian city-states during the Middle Ages and Renaissance, such as Florence, Venice, Genoa and Milan. With the rise of nation states worldwide, there remains some disagreement on the number of modern city-states that still exist; Singapore, Monaco and Vatican City are the candidates most commonly discussed.
