Hypogeum of Ħal-Saflieni - Malta

Thanks to Marta from Italy, i've got my last missing Unesco site from Malta :D The Hypogeum of Ħal-Saflieni is an Unesco World Heritage Site since 1980.

The Hypogeum of Paola, Malta, literally meaning "underground" in Greek, is a subterranean structure dating to the Saflieni phase in Maltese prehistory. Thought to be originally a sanctuary, it became a necropolis in prehistoric times. It is the only prehistoric underground temple in the world.
The Hypogeum consists of halls, chambers and passages hewn out of the living rock and covering some 500m². The rock-cut chambers are of a diverse shapes and sizes and finished to different standards of workmanship. The complex is grouped in three levels – the upper level (3600-3300 BC), the middle level (3300-3000 BC), and the lower level (3150 -2500 BC). The deepest room in the lower level is 10.6 metres under road surface.
It was discovered by accident in 1902 when workers cutting cisterns for a new housing development broke through its roof. The workers tried to hide the temple at first, but eventually it was found.
The Hypogeum of Ħal Saflieni is a very popular tourist attraction. However, because of its age, Heritage Malta (the government body that looks after historical sites) only allows 80 persons per day to visit the Hypogeum. Heritage Malta recommends tourists to book well ahead of time if they wish to visit.