1. INTRODUCTION The megalithic temples of Malta have been dated back to the 4 th millenium BC. The oldest of the major temple sites, Ggantija in Gozo, has been dated, on the basis of recalibrated radiocar- bon dating, to 3600 to 3000 BC, the “youngest”, Tarxien, to 3000 to 2500 BC. This is therefore looking a civilization that lasted at least 1000 years. It is still not clear where it came from and where it disappeared to, and why. The temple sites understandably underwent a number of changes over the 3500 – 2500 BC millenium. The Lower Temple in Mnajdra, for example, belongs to the older Ggantija phase, whilst the Middle Temple belongs to the Tarxien phase. It is therefore not surprising to find a significant difference in the characteristics of the stonework, in the quality of the workmanship, and in the decorative details. On the contrary, it is indeed surprising to observe that the structur- al principles, on which the temples are based, apparently remain so consistent over this period. These principles also appear to be surprisingly sophisticated. To our knowledge the Maltese prehistoric megalithic temples are the oldest expressions of free-standing stone architecture. This extraordinary statement is made even more amazing not only by the fact that more than thirty prehistoric sites have been uncovered in the barely 320 sq.km. that make up the Maltese Archipelago, but also that the structures with similar characte- ristics, found in other neighbouring Mediterranean countries, such as the Balearics, the Iberian Peninsula, or Sardegna, generally have a much younger pedigree, and, in any case, do not have the whole range of characteristics of the Maltese megalithic structures. The engineering of the prehistoric megalithic temples in Malta A. Torpiano Faculty for the Built Environment, University of Malta, Malta ABSTRACT: The prehistoric megalithic structures of Malta and Gozo date back to a civiliza- tion of 4500 to 5500 years ago. Although now in ruins, their longevity is remarkable, and must be due to the inherent durability of limestone, properly selected, as well as to the underlying en- gineering principles and construction. Prehistoric civilizations are often, erroneously, perceived as technologically primitive, however these prehistoric structures are technologically remarka- ble. This paper proposes engineering principles underlying its longevity. Hitherto, many of the features of the extant structure have been explained as having “decorative” functions. The au- thor suggests that these features should be assessed in the light of the possible engineering and constructional processes adopted; this approach is based on the belief that, particularly for civi- lizations in which energy resources were stretched, it would not make “resource” sense, if these features were not there for a specific purpose – it would not be, using modern terminology, sus- tainable.