Back Bay, Boston’s most expensive and prestigious neighborhood, was built on landfill. Its highlights are the Esplanade, a beautiful bike and walking pathway along the Charles River. The Charles River itself has terrific sailing and boating as well. The area is marked by its charming tree-lined streets with rows and rows of late 19th century brownstones. Newbury Street is Back Bay’s premier shopping district and goes hand in hand with the Copley (pronounced Cop-Lee) Mall, an indoor behemoth of a place that seems to take up about as much retail space as the rest of Back Bay’s residential areas. The Public Gardens are a terrific and romantic place to spend an afternoon and if you’re already there, you should cross over to Beacon Hill and have a walk down Charles Street, another charming commercial strip with a flavor all it’s own.