The designation oldest synagogue in the world requires careful definition. Many very old synagogues have been discovered in archaeological digs. Some synagogues have been destroyed and rebuilt several times on the same site, so, while the site or congregation may be ancient, the building may be modern. Still other very old synagogue buildings exist, but have been used for many centuries as churches, mosques, or for other purposes. And some very old synagogues have been in continuous use as synagogues for many centuries.