The Tour Odeon, a double-skyscraper residential apartment block being built by Groupe Marzocco SAM, center, rises above the coast line and residential property in Monaco, France, on Thursday, Sept. 25, 2014. Monaco, the tax haven on the French Riviera, is experiencing a luxury-housing boom that includes the world's most expensive penthouse as developers prepare for an influx of millionaires and billionaires escaping higher taxes or a loss of banking privacy. Photographer: Simon Dawson/Bloomberg via Getty Images
