Henry Mercer loved dogs, and his favorite breed was the Chesapeake Bay retriever. He had many of these dogs, some of which were named Jack, Sailor and Larry. Mercer’s favorite at the time of the construction of the Mercer Museum was Rollo. Mercer allowed Rollo to run through wet concrete in the newly constructed parts of the Museum. His enormous paws left equally large prints, which are still evident to Museum visitors on “Rollo’s Stairs” between the fifth and sixth floors today. Fonthill Castle also features “Rollo’s Stairs” – discover paw prints in the concrete stair treads in the Columbus Room.