Mathilde Wesendonck was a German poet and author. The words of five of her verses were the basis of her friend Richard Wagner's Wesendonck Lieder. He may have been her paramour.
Wikipedia https://en.wikipedia.org/wiki/Mathilde_Wesendonck
Address 1 Schwanenmarkt, Düsseldorf 40213, Germany
Coordinates 51°13'9.662" N 6°46'21.597" E