Quarries for ashlar building blocks are known to exist anywhere where the Phoenicians, Carthaginians and Romans have extended their territorial rule. These can be recognised by the distinctively straight-cut walls from which the ashlar blocks were extracted. Within the open areas of these quarries one can also notice the detachment grooves of the removed blocks. The faces of the quarries are frequently marked by channels that demarcated the blocks to be removed.
A large number of ancient shallow quarries with regular cuts can be found distributed across the Maltese Islands, but they appear more numerous in the north-west part of Malta, especially within the localities of Mellieħa, Rabat, Mġarr, and St Paul's Bay. These quarries are found mainly in Upper Coraline terrain and their configuration, texture, and patina provide enough evidence that they are very ancient features.
The large open area at Għar il-Kbir is surrounded by ancient regular quarries on all of its four sides. All the ancient quarries are shallow and in all parts where they were not reclaimed by agricultural fields one can identify the detachment grooves of the removed ashlar blocks whose size are equivalent to large standard dimensions of building blocks typical of the Phoenician-Punic Roman Periods.
The present agricultural field system in the area seems to have evolved after the ancient quarrying activities. This is attested by the large quantity of cavities which have provided adequate ready-made basins for the agricultural fields. Moreover, there are numerous examples of the detachment grooves that demarcated the extracted blocks underlying the rubble walls enclosing the fields.
The Cart Ruts found in these areas also pre-date the field enclosures as a number of tracks lead straight under the rubble walls and fields.