Posted at Nov 18/2007 06:22PM:
Audrey: Ribat are not specific architectural structures. The term is generally used to refer to a building or city. Originally it specifically referred to sites described as monastery-like shelters for ascetics who would gather there to study, pray and write. The ribat were also fortified against attack, as they were usually located on the frontiers of Muslim territories. A murabit is a person who lives in a ribat. Their purpose in inhabiting a ribat was to achieve a form of baraka (divine blessing), by living on the frontier and engaging in worship and warfare. Murabit thus achieved both the internal and external aspects of jihad by participating in activities at a ribat, as they could follow the tariqa back to Allah through spiritual study and also engage in active fighting.

Posted at Nov 18/2007 06:26PM:
Audrey: Also, Monastir, Sousse (both Tunisian), Alexandria and Beirut were notable locations of rabat. Here is the one at Monastir