By all accounts, Charles d’Este Guelph, Duke of Brunswick (1804-1873), was a bit of an eccentric character.
A German nobleman, he made his vast fortune in Paris before moving to Geneva. The Duke bequeathed his fortune to the city, but there was a proviso. His conditions were the holding of a grand funeral and the erection of a monument in his honour.
And so it came to pass, after much debate, that the first mausoleum was built in the city of Geneva in 1879. And an equestrian statue, naturally, the Duke being an avid horseman.