The four crescent shaped forts of Lunetten have been build between 1822 and 1828 as part of the Dutch Water Line. Forts and fortified towns have been constructed to protect weaknesses in the waterline. Combined with natural bodies of water, it could be used to transform the economic heartland of the Dutch Republic almost into an island.
References:The Château du Lude is one of the many great châteaux of the Loire Valley in France. Le Lude is the most northerly château of the Loire Valley and one of the last important historic castles in France, still inhabited by the same family for the last 260 years. The château is testimony to four centuries of French architecture, as a stronghold transformed into an elegant house during the Renaissance and the 18th century. The monument is located in the valley of Le Loir. Its gardens have evolved throughout the centuries.