Saarlouis is a city in the Saarland, Germany, capital of the district of Saarlouis. Saarlouis, as the name implies, is located at the river Saar. It was built as a fortress in 1680 and named after Louis XIV of France. With the Treaties of Peace of Nijmegen in 1678/79, the Lorraine fell to France. In 1680, Louis XIV of France gave order to build a fortification (to defend the new French Eastern frontier) on the banks of the river Saar which was called Sarre-Louis. France's famous military engineer, Sebastien Le Prestre de Vauban, constructed the city, the plans were made by Thomas de Choisy, the city's first Gouvenour.