Possibly my favorite item in the British Museum is this miniature altarpiece, which, as you can see, opens to show an immensely detailed relief carving, in boxwood, of the Crucifixion. And when I say miniature: the entire object is less than ten inches high. When you see it in person, the spears of the Roman legionnaires are impossibly thin, the detail on the faces impossibly precise. The emotional power of the object is all out of proportion to its size.

Details here.