From the World Heritage inscription:
The monuments that make up this World Heritage site constitute the most characteristic examples of structures representing a major development in the cultural as well as the artistic and technological domains. Professor Lord Renfrew (Cambridge University), one of the leading prehistorians of the present day, has described the group of megalithic temples on the islands of Malta and Gozo as ‘the oldest free-standing monuments in the world’. They are, moreover, remarkable for their diversity of form and decoration.
Being among the remarkable megalithic temples of the Maltese archipelago, the prehistoric ensemble of Ġgantija on the island of Gozo may be favourably compared with the three great temples of the island of Malta: Mnajdra, Ħagar Qim and Tarxien. Within a completely preserved enclosure wall, Ġgantija consists of two temples of multi-foil plan.
The southern temple, with its two elliptical cells, is the oldest; the northern temple, which is small in size, is more recent, although no later than 2200 BC. The ensemble of Ġgantija which serves as a point of archaeological reference – the ‘Ġgantija Phase’ (c. 3000-2200 BC) is one of the most important periods of the Maltese Bronze Age. The complex structure of the cultural group of Ġgantija, the excellent state of preservation of its materials – hard chalky coralline and the softer globigerina limestone – make it an excellent testament of megalithic prehistoric art.
There are human artifacts older than the megaliths in Malta (cave paintings, pottery fragments, etc). However, there are no structures that we know of which are older. That fact alone makes this an incredibly important world heritage site.
There are several monolithic structures around the islands of Malta and Gozo. The primary structure is the Ġgantija Temple on Gozo, which is where the above photo was taken.
Getting to the various structures is not difficult once you are on Malta. The Ġgantija Temple can be reached by bus from the central station in Victoria on the island of Gozo. Likewise it, and the other sites on the island of Malta can all be reached by car or taxi.
While significant, the sites are not actually that large and do not take much time to explore. 1 hour should be more than enough time for any of the sites.