http://agathe.gr/democracy/sources_and_documents.html
Sources and Documents Our understanding of the workings and history of Athenian democracy comes from a variety of sources. Most useful, perhaps, are the ancient literary texts that survive, many of which ... Toward the end of the 5th century, the senate moved to the New Bouleuterion, but the archives stayed behind in the Old Bouleuterion, and the building became known by a new name, the Metroon, named for Rhea, Mother of the Gods, whose cult was also housed in the building.