DAMASCUS (REUTERS).- When French engineer Jacques Montlucon bought one of the famed, centuries-old courtyard houses of Old Damascus six years ago he had no idea it contained an architectural marvel.

But Montlucon, who has restored artifacts from the Titanic and helped rescue goods from a sunken Napoleonic merchant ship, has a knack for uncovering the unexpected.

"I was removing the heavy varnish covering the wood-paneled walls in the iwan (reception room) when figures of painted strange birds, monsters and castles started to emerge," he said, pointing to the fine drawing between the carved wood.

"The paintings are dated 1789, the year of the French Revolution. But who knows how long it had taken for the news to travel from Paris to Syria," he said.

An imaginary black bird pulls a boat. A man points a rifle from the top of a castle on a sea and monsters fly over the water. The wood ceiling resembles an intricate Persian carpet.

"It's a fairytale, but no one yet has been able to explain it," said Montlucon, who first came to Syria in 1965 in a tiny French car and worked in the Middle East over a 30-year career with Electricite de France.

The small house, which has an elegant fountain and a magnificent rooftop view of the Umayyad mosque, is one of the best kept secrets of Old Damascus. Montlucon believes it dates from the middle of the 18th century.

The once walled city, a United Nations world heritage site, is attracting tourists in increasing numbers as Syria, which has been ruled by the Baath Party since 1963, has relaxed entry restrictions and lifted bans on private enterprise.

Unique Paintings
The carved wood, stone and elaborate high ceilings were signs of status at Damascene homes, which later incorporated paintings as the cosmopolitan city interacted more with Europe and Western artists and 19th century adventurers visited Syria.

While paintings of buildings and landscapes can be found at the courtyard houses that have survived neglect and destruction in modern Damascus, the mythically themed paintings at Montlucon's home are unique.

Together with a friend he used cotton buds immersed in basic solvents and simple water colors to restore the room. It took six months -- time-consuming, he said, but not difficult.

"The most important principle in restoration is for it to be reversible, in case you find a better way," said Montlucon, who has restored artifacts from the Titanic using electrolysis techniques and helped rescue items from Le Patriot, a merchant ship from Napoleon's fleet which sank off Egypt.

Behind plain 20th century tiles in the same room, Montlucon also uncovered carved stone walls with mosaic-like Arab patterns, a technique pioneered by the Mamluks, one of the many rulers of Damascus.

Syrian craftsmen had a reputation for carving stone as if they were cutting paper. They flourished during Ottoman rule from the 16th to early 20th century, and incorporated Persian and Western influences, such as baroque into their work.

"The owners of the house wanted to probably hide from the taxman how opulent their property was, or simply tastes had changed," Montlucon said.

Adding his own touch, Montlucon furnished the house with antique Syrian mother of pearl and art deco furniture from the nearby "Thieves Market."

Passing by a pile of rubble thrown out by workers in a nearby house once, he found prized white and blue Islamic tiles. They now grace a wall.

Beit (house of) Jacques was part of a bigger aristocratic house next door that was bought by Noura Jumblatt, the Syrian wife of Lebanese Druze leader Walid Jumblatt, an enigmatic former warlord during Lebanon's civil war who has had uneasy relations with Syria.

Noura's restoration is immaculate, but many of the ancient properties that are being turned into restaurants and hotels in the old city have been restored in a way that experts say may have done irrevocable damage.

Artists who moved to the old Jewish quarter of the city have done a better job at conserving the original work.

Montlucon remembers coming to Damascus to study Arabic 10 years ago and wanting to find out the secrets of the old aristocratic houses whose simple facades of stone and mud hide their magnificence and serenity inside.

The neglect has driven Montlucon, who is in his 60s, to try and save more of the old city. He plans to turn another house, which he just finished restoring, into a center for the preservation of craftsmanship and heritage techniques.

The house, which has mirror work ceilings, belonged to Syrian Bedouin prince Trad al-Milhem, who lived there in the early 20th century. It is probably built on the ruins of an Umayyad palace.

Montlucon said modern development and pollution were two of the main threats to preserving Syria's legacy.

"Syria's heritage without a doubt is one of the richest and most diverse," he said.

"It's based on intangible technical elements which at best may irrevocably change or at worst disappear."

(Editing by Dominic Evans and Paul Casciato)