In 1803, he made a first terracotta model of "Ariadne on the Panther", which he executed in marble between c.1810 and 1814. This is generally regarded as his masterpiece and one of the most important sculptures of the nineteenth century (today in the Liebieghaus Sculpture Collection, Frankfurt).[2] In 1810, the Frankfurt banker Simon Moritz von Bethmann signed the contract for the marble version. He built a small neoclassical museum (known as the Bethmann Museum) in his garden which was completed in 1816 (today Seilerstraße 34).