If you can’t afford to live on the Île Saint-Louis, the next best thing is strolling its streets, browsing the snug antique shops and galleries and indulging in some of M. Berthillon’s famous icecream. The island was a swampy, vagabond-ridden area until the 17th century, when the speculator Christophe Marie transformed it with the hôtels particuliers which make up some of the city’s most coveted real-estate today. Along the main drag, notice the strange perforated spire of Saint-Louis-en-Île, a later addition to Le Vau’s original church, and peek, if you can, at the timber frames of the former tennis court, now an upmarket hotel at number 54. On either side, the quais serve up a feast for mansion-spotters.