UNTERUHLDINGEN, GERMANY—The Pfahlbaumuseum, an outdoor museum on Lake Constance that features reconstructions of Neolithic and Bronze Age stilt houses, will return 8,000 Neolithic pottery fragments that were illegally excavated from Thessaly during World War II. The Greek government seeks the return of all antiquities that were illegally removed from the country during the German occupation. The two countries are also working on an agreement for the protection of cultural goods and the prevention of artifact trafficking.