Wilhelm I, King of Prussia then Emperor of Germany, visited this famous spa on many occasions. Opposite the assembly rooms, near the Roman springs, is a flagstone dated 13 July 1870 commemorating the meeting between Wilhelm I and the French Ambassador, Benedetti, at which the Emperor categorically dismissed French moves to prevent the Hohenzollerns from making a claim to the throne of Spain. The Emperor's telegram, distorted then leaked by Bismark, hastened the Franco-Prussian war of 1870.