The Nebra Sky Disc, discovered by archaeologists on Mittelberg hill, in Germany, is made of bronze and gold. It is the oldest representation of the cosmos in human history. The disc hails from the Early Bronze Age, and its face holds an encrypted code. Though much is known about ancient civilizations in Egypt and Rome, less is known about those of central Europe. In this exhibition, 400 objects paint a panoramic picture of an era that is seldom the center of attention. Lenders span 15 countries, and most of the relics have never before been to Germany. —E.C.