James Mossman grew up in Ontario, but never learned to skate as a child. “That’s why they made me leave Canada,” joked the retired chief investment officer of the Blackstone Group.

A few years later, when Mr. Mossman’s two young sons took up hockey, he decided to give skating a try. Now Mr. Mossman’s nearly 13,000-square-foot, eight-bedroom home in Greenwich, Conn., which is on the market for $11.975 million, has a refrigerated outdoor ice rink in the back yard during the winter months.

The rink, which is about 110 feet long, has a clubhouse for storing hockey gear, and a fire pit and heat lamps that come in handy for frequent skating parties. “People who haven’t skated in 35 years, they go out there and become kids again,” Mr. Mossman, 56, said. “We’ve got music and lights—it’s a really fun thing.” He declined to say exactly how much it costs to maintain a hockey rink, but said his electricity bills have gotten higher because of the refrigeration.

ENLARGE

In the summer, the rink converts to a tennis court. The estate, which sits on about 13 acres, also has an outdoor pool, an observatory with a telescope, an English greenhouse and an indoor rock-climbing wall. Mr. Mossman said when he bought the house for $4 million around 20 years ago, he liked the idea of a large backyard with lots of activities, where “you could just have fun and basically be at camp.”

A highlight was when hockey star Mark Messier, who was visiting relatives nearby, in 2005 asked to use the rink with his nephews. Mr. Mossman and his sons got a chance to play hockey with the former NHL player, who signed the clubhouse door before leaving.

Mr. Mossman said he’s decided to sell the house because his children are grown. But he said he’ll miss all the activities, especially the ice skating. “It’s a little bit sad,” he said. The property is listed with Tamar Lurie of Coldwell Banker Previews International. It’s also being marketed by Ruhm, a California-based creative digital-marketing company.