Cyclopean masonry, used to construct the LH III fortifications on mainland Greece, has been broadly defined as being of large irregular-shaped blocks, commonly of local limestone, unworked or roughly dressed and assembled without mortar, but with small stones set in interstices. Unfortunately, this is the extent to which this masonry has been defined, leaving unanswered questions concerning building style, engineering techniques, and the amount of labour invested in the projects. The heavily fortified palatial/residential complexes of Mycenaean Greece have often been considered the result of an unsettled and aggressive society; however, an investigation into the types and location of the various structures suggest that the walls were designed to conspicuously display wealth. Cyclopean stonework is not confined to the citadels, but includes the elaborate drainage project of the Copais and a system of road networks, both which would suggest a high level of cooperation between communities. Indeed, calculations made in considering resource availability demonstrate that fortifications exceeded all defensive requirements and were probably constructed in then- initial form as part of a programme promoting and strengthening the status of the state through a display of its wealth in large scale building programmes. These monumental fortifications are often believed to have then- origins elsewhere in the Aegean, Cyprus, or the Near East; however, the evidence points to an independent development on mainland Greece. Features of the fortifications are analysed and compared to earlier and contemporary forms of Aegean, Cypriote, and Near Eastern structures in order to understand similarities and/or differences in construction, with a particular emphasis on those structures outside the Greek mainland that have been labelled as "Cyclopean". The conclusion reached is that in each geographical region the fortifications form a distinct group. In order to determine the origins of Cyclopean masonry on the Greek mainland, Cyclopean structures other than fortifications are studied and the masonry style is classified into a typology for an understanding of differences in regional work or date. This information is then used to understand Mycenaean social complexity, defined as the resultant behaviours of individuals or groups functioning within a larger collective assembly whose attitudes and actions, either directly or indirectly, affect the larger community, and to show how previous notions of an aggressive and warring society maybe inaccurate. Although the Mycenaean culture may have been competitive, its means for competition and displays of wealth could only have been achieved through cooperative measures.