The Hegeler Family (then the Carus families) have been working out at home since 1876 in what is thought to be the oldest, privately owned gymnasium in the country.
It also boasts a parabolic arch in its design which was virtually unheard of in private homes. We use to let tours go down into the gym but a visitor tried to crawl up the rope and pulled it out of the ceiling. So now the guest need to stay on the steps.
In the pics below, it is getting a good cleaning. You can see the arch and most of the original weights, skis etc. The pommel horse and medicine ball in the pic are not original to the house. They did have those pieces of equipment in the original gym though. Paul Carus liked to throw the medicine ball around for exercise.