We figured this would be a straightforward question to answer. Not so. It transpires that there are several chandeliers vying for the title of "world's largest", and it's a difficult call to make, since "chandelier" has come to describe a wide array of suspended lighting devices that are not that easy to compare. However, we think, we answered your question accurately, at least by official reckoning.
Some research revealed that Caesars Palace only purports to have the world's largest baccarat crystal chandelier, not the largest outright. But a query to the property revealed that even this is not confirmed: "Like you, we couldn't be absolutely sure," came the response.
According to Wikipedia, the world's largest Bohemian crystal chandelier, a gift from Queen Victoria, is located in the Dolmabahçe Palace (Istanbul). It has 750 lamps and weighs 4.5 tons.
As far as the world's largest is concerned, we believe it was installed inside the dome of Hassan Al-Sharbatly Mosque in Cairo, Egypt last September and the report we read said it is expected to be included in the 2011 edition of Guinness World Records.
Dimension-wise, it's 17.7 meters high, 12.5 meters wide, and with a diameter of 17.6 m, which is more than double the diameter of the previous chandelier registered in the Guinness Book of World Records. It weighs approximately three tons and took at least 90 engineers working collectively for 17,000 hours to complete.
The previous record-holder was "Reflective Flow", located in Quatar's Al Hitmi building, which claimed Guinness World Record status in June 2010. It comprises 2,500 different blocks of light and weighs 19,900 kg, but it's not a conventional chandelier by any stretch of the imagination. It's an "interactive LED light sculpture" made up of 2,300 individually hand-ground optical crystals and it's pretty impressive, although it reminds us of a giant eel.
Melbourne's Crown Casino has what's generally noted as the largest chandelier in the southern hemisphere. Although it's made up of 40,000 crystals, this is another unconventional chandelier, since the crystals are not lit by candles or light bulbs but rather by 10,000 fiber optics placed among them, which interact with two lasers to project animation on the ceiling.
So, what of The Cosmopolitan's impressive and more traditional offering? Our understanding is that the three-story chandelier that adorns the Chandelier Bar occupies 10,000 sq. ft. of space and comprises 2 million glass beads. It's incredible and massive and we're not sure how to compare it with some of the other contenders, but apparently the powers that be have deemed it merely the largest chandelier in North America.
