Għar Dalam (the Cave of Darkness) is a 144-metre limestone cave on the outskirts of Birżebbuġa, about three kilometres west of Marsaxlokk. The site is a paleontological landmark: layers of cave sediment have yielded the fossilised bones of pygmy elephants, hippos, deer, brown bears, and giant swans that lived on Malta during the last glacial period, when the island was joined to Sicily.
The small adjacent museum displays the fossils in stacked Victorian-style cases — extraordinary for the sheer quantity of material packed into one room. A short walkway lets you enter the cave itself for the first 60 metres. The combination of the cave and the museum makes a good thirty-minute stop on a south-Malta circuit.