Carl Hagenbeck was a German merchant of wild animals and humans who supplied many European zoos, as well as P. T. Barnum. He created the modern zoo with animal enclosures without bars that were closer to their natural habitat. The transformation of the zoo architecture initiated by him is known as the Hagenbeck revolution. Hagenbeck founded Germany's most successful privately owned zoo, the Tierpark Hagenbeck, which moved to its present location in Hamburg's Stellingen district in 1907. He was a pioneer in displaying humans next to animals in human zoos.

https://en.wikipedia.org/wiki/Carl_Hagenbeck