Lots of archaeologists theorize about what was being transported along the tracks (i.e. water, food, goods, stone, etc.) Most agree that the weight of the load contributed to the depth of the tracks. In the background is a big clue. A modern quarry. Clapham Junction has the largest deposit of Upper Coralline Limestone (the hardest and most durable stone) on the eastern part of the island of Malta. It’s not hard to imagine that over the millennia, many cultures have found this a prime spot for mining their building blocks.