The history of Aden as a port goes back a long way; it is mentioned in the Biblical Book of Ezekiel (c. 6th century BC). There is a collection of pre-Islamic artifacts in the National Museum of Antiquities near Tawahi Harbour. Crater, the oldest part of the city, lies in the crater of an extinct volcano and is where the most ancient constructions in Aden may be seen. These are the Aden Tanks, manmade reservoirs, partly cut out of the rock, with a storage capacity of 50,000,000 liters. When it rains, the upper basins fill up first and then overflow into the lower basins. Also in Crater may be found the Ethnographical Museum and the Military Museum. The 14th-century Mosque of Sayyid Abdullah al-Aidrus commemorates the patron saint of Aden. In Ma’allah, the visitor can see traditional Arab boats. To the south of Aden is Little Aden, also in the crater of an extinct volcano; this is an area of small fishing villages in sheltered bays, with several superb beaches fringing the Indian Ocean.