Other causes may have been famine, social disruption in response to an oppresive priesthood, and the arrival of foreign invaders. On the islands of Malta and nearby Gozo, the remains of 50 temples have been found, with 23 in various states of preservation. No particular pattern emerges from the distribution of these temples and this may be explained by the probability that numerous temples were destroyed in antiquity and that others remain to be discovered. There are also numerous menhirs and dolmens scattered across the two islands, but their spatial relationship to the larger temple complexes has not been studied in any detail. The Herculean outer shell of walls are formed of great blocks of stone propped on end or on edge as orthostats.
Internal walls are either of piled rough coralline blocks, or well-cut slabs set as orthostats.
All walls consist of two faces, the space between being packed with earth or rubble. Doorways and passages all use the trilithon principle, two orthostats parallel to each other to support a horizontal lintel. Frequently doorways consist of a 'porthole', in which access is through a rectangular hole in the center of a slab. Both of these stones were deposited in the Miocene geological period. The construction tools available at the time were hand-axes made of flint and quartzite, knives and scrapers of volcanic obsidian, wedges of wood and stone, hammers of stone and levers of wood.