The 26,190-square-foot Mansion on Madison, formerly the Villard Mansion, was reintroduced to the real estate industry last week. Previously railroad tycoon Henry Villard’s mansion, the grand residence at the New York Palace Hotel is being transformed by owners Northwood Investors. Marketed as a flagship retail location or a unique corporate office, the Mansion on Madison drew a large crowd last Thursday night for a “Midwinter’s Bash.” Jedd Nero, the executive vice president of retail services at CBRE, was on hand to point out some of the building’s more unique features.