 After the Franks were driven from the Holy Land in <unk> , European familiarity with the castles of the <unk> declined . It was not until the 19th century that interest in these buildings was renewed , so there are no detailed plans from before 1837 . Guillaume Rey was the first European researcher to scientifically study Crusader castles in the Holy Land . In 1871 he published the work <unk> sur les monuments de l <unk> <unk> des <unk> en <unk> et dans l <unk> de <unk> ; it included plans and drawings of the major Crusader castles in Syria , including Krak des Chevaliers . In some instances his drawings were inaccurate , however for Krak des <unk> they record features which have since been lost . 
