What would you do if you had $20 billion?  What about building a $1 billion skyscraper in the middle of Mumbai to celebrate your wealth?  Maybe you'd create a 60-storey building but then only put in 27 stories and make everything double height?

That's pretty much what Mukesh Ambani - an Indian billionaire is doing (Read about it here and here).  Here's an image of his creation, the Residence Antilia: