The Hal Saflieni Hypogeum is a unique prehistoric monument which bears testimony to a civilisation which has disappeared. The subterranean site was discovered during the building of houses in Paola at the turn of the twentieth century, reported to the authorities in 1902. The Hal Saflieni Hypogeum is in close proximity to the contemporary megalithic complex of Tarxien and ceramic evidence point to the Ggantija, Saflieni and Tarxien phases, indicating that the main periods of use may be dated between 3,600 - 2,500 BC (Evans, 1971).

The Hal Saflieni Hypogeum is a series of rock-hewn chambers on three different levels. The Upper Level, may have had a monumental structure marking its entrance (Cutajar 2000), but must have sustained damage during the building of the overlying houses. In prehistoric times, the upper level was exposed to the natural elements, bathed in natural sunlight and moonlight.

The Middle Level houses the most elaborate chambers, hewn using only stone and bone tools, resulting in stunning work showing high quality skill and dedication. The innards are sculptured in the same form as the megalithic temples that are above ground, with faint red ochre spiral designs in red ochre still adorning the walls and ceiling and is the only surviving example where one can still observe in situ the colourful embellishments of such structures. The Lower Level is deemed to have been the actual burial layer with small skeletal bones from the circa 7,000 cadavers believed to have been buried in the hypogeum.

Unlike other recent catacombs, there are no actual cradles where bodies could be laid in death, so except for the excavations of the dated bones there is scant evidence that the dead were laid inside the Halsaflieni Hypogeum.