Move over Explorer of the Seas: you will soon be surpassed! Carnival Corporation has finally signed a deal with a shipyard -- France's Alstom Chantiers de l'Atlantique -- to build what it says is the largest ocean liner ever constructed. The cost? About $780 million to build the much-hyped Queen Mary 2 for Cunard Line. And the ship’s gonna be a biggie, weighing 150,000 tons and rising to the height of a 23 story building. A true transatlantic cruiser, she’s also being built for speed -- reaching up to 30 knots. Lengthwise, she clocks in at 1,132 feet.