The Ben Ezra Synagogue used to be a Christian church and was founded in 882 The church was purchased by Abraham Ben Ezra, for 20,000 dinars. Abraham Ben Ezra came from Jerusalem during the reign of Ahmed Ibn Tulun. The church was turned into a synagogue and was a place of pilgrimage for North African Jews and the site of major festival celebrations. The synagogue had numerous renovations and was used again starting at 1892. During the reconstruction, a medieval Geniza (a hiding place for sacred books and worn-out Torah scrolls) was discovered, revealing thousands of original documents from the Middle Ages. Now, the Ben Ezra Synagogue is a historical monument and a most-visited Jewish site in Cario. You have to pass through securtiy to visit but you can get a guided tour.