The 42-room mansion in the mountains near Aspen has a roller coaster past: Teddy Roosevelt stayed at the estate during a hunting trip after he left the White House; oil tycoon John D. Rockefeller did too. But it was nearly abandoned after a mining bust, and some say the cigar-smoking ghost of its builder, coal baron John Cleveland Osgood, still haunts the halls.
''We're hoping the right buyer will come by and recognize the need to preserve a very important part of Colorado history and a very important part of U.S. history,'' Internal Revenue Service special agent Jim Harrison said.
Lined with antiques and surrounded by a carriage house, barn and other outbuildings, the castle and 149-acre estate last sold in 2000 for about $6 million. Harrison declined to say what it is worth today.
Federal agents seized the castle in March 2003 during a federal investigation into an international Ponzi scheme. The IRS also seized about $17 million in cash from various bank accounts and race cars worth $2 million.