A brownstone at 501 Garfield Place in Park Slope has sold for $800,000, half off its former sales price, according to a tipster who alerted us to the sale. The property was not listed, but formerly changed hands for $1.6 million in 1996, according to PropertyShark. It was an arm’s length transaction, said our informant, who added that he thought the banking crisis in Cyprus might have had something to do with the sudden drop in value. Formerly a Building of the Day, the brownstone was designed by Montrose Morris and located just a stone’s throw from Prospect Park on one of the best blocks in Park Slope. Inside, the brownstone’s original details were perfectly preserved, with new mechanicals, including updated kitchens and baths. “The marble went on for acres and the back wall was blown out with custom-made iron windows,” said someone who saw the interior before the sale. “I’m not sure if the seller got in over his head with the renovations — or maybe conforming to Landmarks’ requests for historic windows was the last straw.” A real estate agent we contacted who requested anonymity, said “In 30 years of selling real estate, I’ve never seen anything like this. Run for the hills.” We are looking into emigrating to Canada. Does anyone know more?