The Ice Age had a great impact on Malta not only in shaping its topography but also on its flora and fauna. The climate in those days was milder and much wetter, almost tropical. The vast amount of water from heavy rainfalls was responsible for carving up the landscape and forming the valleys, as we know them today. Underground caverns and caves were also hollowed out.
One such cave is that of Ghar Dalam, perched on a low cliff-face at the mouth of Wied Dalam at Birzebbuga on the south of Malta. It is good example of the KARST phenomenon erosive process within the Lower Coralline Limestone layer.
Today Għar Dalam is considered to be one of the oldest caves in Maltese Islands. Evidence of its remote antiquity are the huge stalagmites and stalactites located in the first quarter of the cave. This cave was formed by the action of rushing waters that eroded the soft limestone forming a long phreatic tube. An overlaying river running down towards the sea gradually ate its way into, through, and well beyond the subterranean tunnel, reaching ultimately the level of the present valley bed. The two ends of the tunnel were thus left perched high on either side of the valley. One end is now Għar Dalam, whilst the opposite end is known simply as 'the Second Cave'.
Source: Heritage Malta