They are considered masterpieces, because the caves are actually man-made hollows in solid rock, from which a complex of architecturally elaborate temples and monasteries has been carved with simple instruments.
The caves are quite simple but were carved with complex instruments.
mnli hypothesis: The caves are quite simple but were carved with complex instruments. premise: They are considered masterpieces, because the caves are actually man-made hollows in solid rock, from which a complex of architecturally elaborate temples and monasteries has been carved with simple instruments.