Al- Ulchaidar is one ofthe outstanding defensive constructions. It is also a distinctive military design not only in Iraq, but in the Arab and Islamic werld . It stands on a commercial route connecting Iraq with the outside world Along this route there were many constructions. which were important stations for travellers and caravans such as Atshan and mu jdah . Investigation and excavation affirmed that it is an Islamic constuction dates back to the second half of IIijrah century . It is rectangular in ahape of 176 M. Length and 146 M . width, includes the main hall, the big Iwan, the reception hall and the servant houses .