Restoration architect Edward Said, of the Fondazzjoni Wirt Artna (Malta Heritage Trust), describes the discovery as "just the tip of the iceberg."
Said suspects the tunnels formed part of a state-of-the-art plumbing system, complete with ancient passageways for access and maintenance.
Thousand-Year-Old Fighting Force
Also known as the Knights Hospitaller and the Order of St. John, the Knights of Malta, established in 1099, gained a formidable military reputation as enemies of Muslims during the Crusades, a series of Christian military campaigns that originally had the goal of capturing Jerusalem.
In 1530 Holy Roman Emperor Charles V offered the knights the island of Malta for the princely sum of one falcon a year.
The Christian order, though vastly outnumbered by Ottoman Turks, triumphed in the Great Siege of Malta in 1565.
The experience, though, inspired them to found the fortress city of Valletta on a high peninsula that was secure but lacking in natural water sources.
Water security was a major priority during the city's construction, the goal being to maintain the supply even during future sieges, according to Said.
"They soon realized that the rainwater and the wells they had were just not enough," he said.
Water was therefore transported to the city from valleys to the west via an aqueduct, the remains of which still stand.
The Palace Square location of the newfound tunnels supports the idea that the network was intended for water, the team said.
The tunnel apparently fed a grand fountain in Palace Square via the underground reservoir. The fountain was later moved when the British ruled the island, from 1814 to 1964.
"This fountain marked the very important achievement of getting water to the city," survey leader Borg said.
Centuries-old lead pipes and metal valves for operating the fountain have been found, according to Said. The tunnel's connecting branches may have included service passages used by the Knights' chief hydraulic engineer, or fontaniere.
"Together with his team, [the fontaniere] was in charge of monitoring and maintaining the fountains and conduits," Said added. "They were also responsible for switching off the fountains at night."
Knights of Sanitation
Other rumors of underground Valletta include a secret carriageway from the city to the palace of the Roman Catholic inquisitor—charged with rooting out heretics—under Valletta's harbor.
Such tales of secret military passages have more solid foundations, according to Said, since underground passages do run beneath the battlements protecting Valletta's landfront.
But Said suspects many of the subterranean legends spring from water-supply and drainage tunnels.
Valletta was hit by plague in the 17th century, when the 1340s Black Death epidemic still loomed in people's minds, he said.
"They wanted to make sure this problem never happened again," Said added.
In fact, the city's plumbing system was highly advanced for the 16th and 17th centuries, he noted.
The Knights of Malta Today
In 1798 Napoleon banished the knights from Malta. Today, based in Rome but still called the Order of Malta, they are involved mainly in humanitarian enterprises.
Still, this month the Maltese government announced that, following the discoveries, the underground-garage plan has been shelved.
A new fountain, based on the original, is slated for the square, and Said is hopeful that the secret tunnels will eventually be opened to the public—one more reminder of the knights that still bear the island's name.
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