Shell Petroleum plans to build a floating natural gas refinery off the coast of Australia that they say will be the largest floating object the world has ever seen.
When it's completed aroud 2017, the Prelude FLNG will be the largest thing that has ever failed to sink, at 1,600 feet long with a displacement of 600,000 tons. It will require some 260,000 tons of steel to construct, which happens to be four times as much as what went into building the Sydney Harbor Bridge, if that's a useful metric for you.
The ship (or maybe, semi-portable island) is designed to sit above oceanic natural gas fields, refining the gas and cooling it down to -260 degrees Fahrenheit for storage and transport. What it's not designed to do is go anywhere. Despite the fact that a big advantage of things that float is that they're mobile, Shell plans to leave the plant moored in the same spot off the northwest coast of Australia for the next 25 years. Australians shouldn't worry, though: the Prelude FLNG is apparently be able to withstand multiple Category 5 cyclones, although there's no word on what happens if it gets struck by an iceberg on a cold April night.