Billionaire Koch Brother Lists Aspen Mansion For $90 Million

William Koch, the billionaire brother of Tea Party darlings David and Charles, has listed his expansive Aspen ski mansion for $89.9 million, according to The Aspen Daily News (via Curbed).

Koch bought the 55-acre property, formerly a hotel, in 2007 for $26.4 million. He transformed it into a stunning ski house with 15 bedrooms, a gym, and several guest houses.

The home was renovated by architecture firm Rowland + Broughton, which has pictures of the interior.

Compared to his politically minded brothers, William is relatively private, though he does have some interesting hobbies. A fan of the Old West, he's currently building a replica of an entire western town to house his large collection of memorabilia, and once paid more than $2 million at auction for a rare photo of Billy the Kid.

Last year, Koch spent nearly $20 million on the Cape Cod estate formerly owned by the Mellon banking family.