(IDEX Online) - De Beers heiress Rebecca Oppenheimer is selling her remarkable off-grid home, a property described as "Guggenheim Museum meets UFO".The self-sustaining six-bedroom, mansion, set in 85 acres of land in Tenino, Washington, USA, has a saltwater pool, barn, chicken coop, honey bees (and bee keeper), and is powered by solar and geothermal systems.The 8,462-square-foot main house is designed as a three-dimensional, eight-point star, inspired by the Garden of Cosmic Speculation, a sculpture garden in Scotland created by American landscape architect and theorist Charles Jencks.Oppenheimer, granddaughter of former De Beers chairman Harry Oppenheimer, has moved back to South Africa following a divorce.She is a trustee of the Oppenheimer Memorial Trust,, where she is "focused on finding unique solutions to the diverse challenges of South Africa, and the wider African continent" through philanthropy and early-stage investment.Agents Morrison House Sotheby's International Realty, in Washington, describe the property as a "flowing modern, circular home atop 85 acres of stunning land with sustainable gardens, saltwater pool, separate 3 bedroom guest house, and archery range. "Intentional less is more, curvy, and plush custom rounded furniture. Environmentally friendly and self-sustaining with geothermal/solar systems allowing for nearly off-grid living. Double gated land mass gives serenity, privacy and presence with nature."The property will be auctioned. Bidding is from 20 to 27 April. It is listed online at $5,950,000.Pic courtesy Morrison House Sotheby's International Realty