The Perdido Oil Platform was the world's deepest production and drilling facility when production started in March 2010 in the Gulf of Mexico (second deepest now). It's one of the most advanced feats in modern engineering, producing 100,000 barrels of oil and 200 million cubic feet of gas each day. As a production hub for three fields, it's the first to separate oil and gas on the seafloor. This structure is as tall as the Eiffel tower and floats in some of the deepest waters in the world currently functioning in 7,800 feet of water. The three-deck topside sits atop the world's largest spar moored by nine two-mile long tethers to the seafloor. Cost to build: $3 billion.