The water clocks of the 12th-century Islamic scientist Ismail Al-Jazari may be regarded as among the most outstanding engineering masterpieces in the history of science and technology in Persia. His other works testify to his remarkable ability in design methodology and in different aspects of mechanical engineering design and manufacture such as robotics, fluid mechanics, strength of materials, and statics. In this study in experimental archaeology two of his water clocks - namely the dragon clock and the peacock clock - were considered for the purposes of making working reconstructions. The historical background, design details, and a technical and comparative analysis of these inventions are presented here. Replicas were constructed in accordance with the indications provided in Al-Jazari's A Compendium on the Theory and Practice of the Mechanical Arts and tests have shown that both clocks operated exactly as described in his book, and with an acceptable degree of precision.