Għar il-Kbir is a set of large caves that were probably initially formed by rain water percolation through the limestone. In time evidence shows us that they were further enlarged by humans as the caves had served as troglodyte dwellings for several centuries. At some point in history part of the caves' roofs seem to have collapsed.
The place-name Għar il-Kbir is derived from these large troglodyte caves. The toponym Għar il-Kbir appears in a late medieval deed dated 18th November 1467 in the acts of Notary Luca Sillato which mentions "the large caves at Rabat situated in a large open space".
During the 16th Century it is noted within a number of deeds that some inhabitants used to reside in the caves and in the surrounding areas.
Within the book named "Descrittione di Malta Isola nel Mare Siciliano" published in 1647 by Gian Francesco Abela, he states that the caves at that time were inhabited by 24 families, amounting to about 117 people together with their many animals.
How early caves had been used as dwellings in not yet known, as they were never scientifically investigated. But what is for certain is that they remained inhabited until 1835 when the British Government issued an order to the residents against their will to resettle at Siġġiewi as the caves were considered inadequate for habitation. However, efforts to document this from contemporary literature has been unsuccessful.
Source: Heritage Malta