The Wikipedia article of the day for July 3, 2017 is Castle.
A castle is a type of fortified structure, generally built in Europe and the Middle East during the Middle Ages. Usually the private residences of lords and nobles, castles ranged from hill forts and country houses to expansive keeps surrounded by curtain walls and fortified towers. After the fall of the Carolingian Empire in the ninth century, castles were used for defence, as bases for raiders, as centres of administration, and for controlling trade routes. As symbols of power, some grand castles had long winding approaches that dominated their landscape. In the late 12th and early 13th centuries, a scientific approach to castle defence emerged, leading to the proliferation of towers, with an emphasis on flanking fire. Many new castles were polygonal or relied on concentric stages of defence that could all function at the same time. Castle building began to decline in the 15th century, when artillery became powerful enough to break through stone walls. In the 18th and 19th centuries, mock castles with no military purpose epitomized the Romantic revival of Gothic architecture.