Valletta's underground features include crypts, cellars, and war shelters, but the most popular feature remains the last train station of the railway system, with its entrance situated just beneath city gate.
Said noted that ideas to extend the underground service down to Fort St Elmo had also been floated at the time but the project never took off.
When its time serving as a train station was up with the phasing out of the railway service in 1931, the area was turned into an underground cinema and there was even a proposal to turn it into an ice-skating rink. However, it soon quite unexpectedly served as an air-raid shelter for 5,000 people.
After the war, the versatile space was turned into a garage, and it was only recently that it was transformed into parliamentary archives and conference rooms.
Fascinating sewage system'
But for Said, the most fascinating feature in underground Valletta is the sewage system, which first started taking shape when the Knights set their eyes on Mount Sceberras.
"It might not be appealing to many, but it was a very innovative system and similar to that in Rome. It was designed by engineers who also insisted on the building of wells under dwellings to store water not just for the households above but also as backup in case of a siege.
"One of the main challenges for these engineers was the topography, which included five valleys across the peninsula. The contractors of this mammoth project were Maltese, meaning the Knights relied on the skill and knowledge of local tradespeople who understood the Maltese resources and stone.
"We could learn a lot about the hard work, thought and technology invested in the building of the system."
The British went on to build on the Knights' sewage system, changing the flow and exit of drainage with the help of a pumping system.
Underground Valletta also hosts a separate hierarchy of passageways that led troops from the capital - through the ditch - into Floriana.
"Underground Valletta has always fascinated people, and tales about what lies underneath the capital are abundant.
"Some say there is a series of passageways leading from Valletta to Tigné Fort and Manoel Island, but these have never been located. Others claim there are huge rats and crocodiles living under the city. Perhaps a folklorist should carry out research into this matter."