When Porter and Hollister Hovey first walked into the Romanesque Revival townhome at 857 Carroll Street in Park Slope—which they were getting ready for sale as part of their work with Hovey Designs, the staging company they co-founded—they fell in love. Not only was the home vacant, which the sisters almost never see, but the turn-of-the-century details were original—another rarity. "To decorate the whole home was such an incredible opportunity," says Porter. "And that started the idea of wanting to do something fun." The sisters came up with the concept for a pop-up shop in the for-sale mansion, and quickly pitched it to Ari Harkov, the listing agent on the $4.695 millionn property. While he wasn't sure if the price or the dead real estate period—winter—would require an extra something special, he jumped at the chance, as did the seller.