On September 16, the New York–based real-estate specialist Concierge Auctions—in partnership with the Aspen, Colo., realtors Joshua & Co.—will auction a secluded haven for equestrians and outdoor enthusiasts located 30 minutes northwest of Aspen. Named Peace Ranch, the approximately 600-acre property lies surrounded by over 10,000 acres of the White River National Forest and features five new or recently renovated houses that range in size from the one-bedroom, 1,156-square-foot Ute cabin to the five-bedro…