new york reliance industries chairman mukesh ambani skyscraper residence mumbai expensive billionaire home world grant forbes list also includes steel tycoon lakshmi mittal houses london ambani skyscraper home antilia named mythic island atlantic tops forbes list expensive homes world deed of conveyance outrageously expensive property world still belongs mukesh ambani antilia mumbai forbes said adding world expensive home alir away construction costs report range billion two billion house six stories underground parking three helicopter tablet reportedly requires staff keep run putting antilia scale price perspective forbes compared world trade center tower stands near ground zero manhattan million square feet office space reportedly built two billion dollars mittal houses london kensington palace gardens occupy spot list expensive billionaire homes world steel magnate believed three homes street known row including mansion near israeli embassy forbes said home rumoured purchased son sold elude fund billionaire noam gottesman value theater million dollars reportedly sale some other house owned mittal upscale street purchased nearly million picked foot mansion billionaire bernie ecclestone pouring millions renovation key taj mittal house bedrooms pool marble sourced quarry taj mahal forbes said continues list homes owned billionaires stacking although market cooled bit properties trading hands million mark kicked bang london set new tape three plate trade million far class us alone forbes said second localize name leopolda home brazilian philanthropist social figure lily safra france forbes said estate reportedly one several waterside domicile king leopold ii belgium built many mistresses set acres massive home valued million dollar sign time russian billionaire mikhail prokhorov tried buy expensive billionaire expensive united states home american english investor businessman provos rennert sagaponack new york value pegged million tentative tax assessment