A GLASS ALTARPIECE

Behind the truly forbidding, massively rusticated facade of Palazzo Pitti in Florence lie the remnants of the delights of the Medici collections, the choicest of which are in the Museo degli Argenti (a rather understated name - Silverware Museum - for what is really a treasure chamber.) The vast frecoed rooms of the ground floor hold incredible things: endless ancient Roman agate or bloodstone cups engraved with Cosimo or Lorenzo's initials; roomfuls each of amber, rock crystal and pink quartz objects; on and on. Upstairs, a series of small rooms shows the famous jewels and cameos. The last one of all has a case with 28 Nuremberg turned ivory cups of incredible complexity, and this...

This altarpiece, presumably from a private chapel, is completely made of glass. Within a complicated wooden frame, against painted backgrounds, are scenes from the Passion of Christ acted out by tiny, inch-high glass figures. Made around 1580 in the Innsbruck Court Glassworks of Ferdinand of Tirol, the Hapsburg archduke who ruled a mountain dukedom from his eccentric and delightful Schloss Ambras. Other pieces of his glass are still at Ambras, and in other collections, but this must be the biggest and most complex.

Ferdinand was a younger son of Emperor Ferdinand, and great-grandson of Maximilian I. Like a lot of his collections, the altarpiece is charmingly kitsch and folksy, with a childishness to the figures and a playful inventiveness to the scenes of crucifixion, resurrection, and so on. Sprinkled with dainty flowers and gambolling puppies, in ever-bright colours and sparkling gold, the piece gives you a great sense of the happy, slightly odd world that he created.