Art: Sequestered Treasure

The façade that Florence's Palazzo Capponi presents to the street is tawny and severe. Unlike Germanic peoples, the Italians built their palaces with austere exteriors, content to have the opulence displayed within. But for the past 15 years, the Palazzo Capponi has defended from public gaze a greater treasure than most. Locked up there was the collection amassed by the late Count Alessandro Contini-Bonacossi. No outsider knew exactly what it contained and the only people with access to it were the dead count's heirs and a handful of their friends.

The collection has been...