Andrew Carnegie used the third floor of his Fifth Avenue mansion as a gymnasium where he practiced his putting. The current owner, the Cooper-Hewitt, National Design Museum, plans to put a small mini-golf green there on Tuesday when the news media gets a preview of the mansion’s nearly completed $91 million renovation.

The gesture is partly a playful way to honor a piece of the building’s history. But it also represents a larger message that the museum is trying to send as it reopens later this year after three years of being closed: This institution, which highlights the importance of design in everything from architecture to umbrellas, can be fun for all kinds of visitors — not just specialists.