Lake Tana, the largest lake, in Ethiopia is the source and from where the famed Blue Nile starts its long journey to Khartoum, and on to the Mediterranean. The 37 islands that are scattered about the surface of the lake shelter fascinating churches and monasteries, some of which have histories dating back to the 13th century. However, it should be noted that most of the religious houses are not open to women. The most interesting islands are: Birgida Mariam, Dega Estephanos , Dek, Narga, Tana Cherkos, Mitsele Fasiledes, Kebran and Deber Maryam.