(IDEX Online) - The new Surat Diamond Bourse (SDB) has officially been recognized by Guinness World Records as the largest office building in existence."The sprawling complex boasts an incredible 659,611 m ? (7.1 million sq. ft) of floor space, spanning 35 acres of land, surpassing the USA's Pentagon as the world's largest office building," says Guinness in an announcement on Tuesday (22 August).The Pentagon, HQ of the US Defense Department, has just over 6.6m of floor space.India's Prime Minister Narendra Modi is due to inaugurate the new bourse on 17 December.SDB, built at a cost of $388m, will challenge the dominance of Mumbai's Bharat Diamond Bourse, currently the world's largest diamond bourse and home to around 2,500 traders.Surat has long been the capital of diamond manufacturing, handling over 90 percent of all the world's gems, but the trade has been centered in Mumbai, a five-hour drive away.SDB comprises nine 15-floor interconnected towers, - each connected to a central spine. Despite its vast size, visitors can walk to any part of the bourse from the entrance in no more than seven minutes.Pic courtesy SDB