Christie's International Real Estate wants to build the world's first portable, eco-friendly private islands, the company announced this week. The initiative allows buyers to order customized, self-sufficient islands they can dock anywhere in the world -- Miami, Dubai, New York, you name it. Christie's says buyers have total control over the size, shape and style of their floating habitat, all of which are completely self-sustainable. Called Amillarah Private Islands, thedevelopment is designed by Dutch hydro architect Koen Olthuis, Christie's says, and will be marketed to affluent islanders looking for a second home. And unlike many second-home purchases, the islands are not designed for yield, the site says, but prestige. It's the "ultimate trophy asset," the site says, with rumored price tags starting at $12.5M, "but financial return is not the primary motivation." A bunch of luxury islands scattered around the oceans could cause an environmental nightmare, but Koen says the island homes carry state-of-the-art green technology -- including artificial reefs that last up to a century -- and keep environmental impact at a minimum.