A detailed map of the subterranean tunnels, crypts and foundation waterways which run beneath Valletta’s hustling and bustling streets is being compiled by a team of architect-cum-historians, in the hope of opening parts of the “unknown city” to the public.

Architectural historian Edward Said’s new organisation, Underground Valletta, has for the past year explored some 130 underground spaces in the capital city, ranging from air-raid shelters and five-storey wells, to complex tunnel networks connecting the various palaces and arterial roads.

“This is our mission and we are committed to discovering more, as there is so much left which we do not yet know,” Mr Said told the Times of Malta.

He was speaking from the sidelines of the NGO’s inaugural activity held earlier this week in the tunnels beneath the Auberge de Castille. After a brief lecture on the history of Valletta’s first underground spaces, such as the caverns at the cliffs of Mount Sciberras all the way to the military spaces used during the Cold War, Mr Said gave some 150 curious visitors a tour of the tunnels connecting the Auberge de Castille to the Auberge d’Italie which today houses the Tourism Ministry.

This is our mission and we are committed to discovering more, as there is so much left which we do not yet know

Perhaps the most compelling of the passageways, Mr Said believes, is the 16th-century sewage system, which runs beneath the entire Valletta grid.

The complex system was dug out of the foundation of the city and much of it is still in use today.

Beneath some of the larger squares in Valletta is a collection of 12 reservoirs, some several storeys deep. Mr Said said these were designed by the knights for a city under siege and could support a population of 40,000 for some four months.