The world’s tallest building is the Burj Khalifa, which reaches 2,716 feet, 6 inches (828 meters) into the sky. The skyscraper was developed by Emaar Properties, and officially opened in Dubai, United Arab Emirates, on January 4, 2010. The building has once again given the Middle East claim to Earth's tallest freestanding structure; the Great Pyramid of Giza claimed this distinction for almost 4,000 years, before England's Lincoln Cathedral claimed the title in 1311.
The Burj was constructed in about six years, with an estimated cost of $1.5 billion. It employs a unique tubular design, and, proportionally, the building requires only half the steel in the Empire State Building. Still, the spire of Burj Khalifa alone consists of more than 4,400 tons (4,000 metric tonnes) of structural steel.
The Burj Khalifa was intended to be entirely residential when designed, but it eventually became a mixed-use building, with the world’s highest residential floor. The building, it should be noted, has only the second-highest observation deck in the world; China’s Canton Tower takes the cake in that category.
Several factors must be taken into consideration when naming the world's tallest building. Some say that only the habitable part of a building should count, no cheating by putting tall spires on top. Others say that the submerged portions of structures rising from water should be included in their height measurements.
Some of the other tallest buildings include the CN Tower in Toronto at 1,815 feet (553 meters), the tallest structure in the Western Hemisphere, and the Petronius Platform, which stands 2,000 feet (610 meters) off the sea floor. The Ursa Tension leg platform, an oil-drilling structure in the Gulf of Mexico, rises 4,285 feet (1,306 meters) from the sea floor, so some say that it’s actually the largest structure in the world. Most architects agree that the tallest building must be on land, however.
And, in case you’re anxious for a dip, the Burj contains the world’s second-highest swimming pool on floor 76; the highest in the world is located on the 118th floor of the Ritz-Carlton Hotel at International Commerce Centre in Hong Kong.