Its gothic twin turrets and stained-glass window featuring a six-pointed star look out from a hillside over a town in south Wales. A Welsh dragon decorates the building’s gable. But rooms that once resonated to the murmur of prayers and readings from the Torah are abandoned; windows are broken, plaster is crumbling and the roof is open to the sky.

But now the Old Synagogue in Merthyr Tydfil, built in the 1870s, could be reborn. It is part of an extraordinary scheme – to be launched this week by the historian Simon Schama – to map more than 3,300 historic synagogues across 48 European countries, and restore the most significant sites.

The synagogue in Merthyr Tydfil was the centre of a community of around 400 Jews, many from eastern Europe. Its members ran a button factory, a chocolate business, a betting shop, property companies and other local enterprises. The annual Jewish Ball was attended by many of the town’s citizens, Jews and non-Jews.

But by the 1980s, a minyan – a quorum of 10 men – could no longer be reached, and the synagogue was sold. The grade II-listed building became a Christian centre and later a gym; today it lies empty and vandalised.

Now, however, there is hope that it will be preserved and restored as a Jewish museum, part of the scheme being rolled out this week. The project, commissioned by the Foundation for Jewish Heritage, has identified synagogues built before the second world war, from Cork in Ireland in the west to Vladivostok in Russia in the east. Each has been catalogued with construction dates and materials, the Jewish community it served, its present use and condition, and a “significance rating”.

Facebook Twitter Pinterest Simon Schama. Photograph: Graeme Robertson/The Guardian

Schama will launch the project in parliament on Wednesday with the backing of more than 40 high-profile supporters including Downton Abbey creator Julian Fellowes, architect Daniel Libeskind, television newsreader Natasha Kaplinsky, artist Anish Kapoor, authors Linda Grant and Howard Jacobson, and former government ministers Malcolm Rifkind and Tristram Hunt.

Before 1939, there were an estimated 17,000 synagogues across Europe, but the majority have been lost. Of the 3,318 surviving buildings, only 718 still function as Jewish places of worship; others are abandoned, in ruins or used for other purposes such as warehousing, factories, restaurants and theatres. One houses a swimming pool; others are funeral homes or fire stations.

The project faced “special challenges around Jewish heritage”, especially in eastern Europe, said foundation member Michael Mail. “The Holocaust was followed by communism. Many buildings were abandoned and essentially lost their communities of users. In preserving these buildings, we also preserve the stories of the communities that for hundreds of years were the heartlands of the Jewish people. These places can serve as profound portals into the worlds that were once there.”

The inventory was undertaken by the Center for Jewish Art at the Hebrew University of Jerusalem, assisted by heritage experts in individual countries.

“We can’t save them all, so let’s save the best, the most important, the most at risk,” said Mail. “We’ve homed in on 160, and narrowed those down to 19 that we’re particularly looking at, where there’s a good chance of saving and restoring the buildings. Each one of those has a different story. In many cases, these buildings are the last witnesses to a Jewish life that was. This is not just Jewish heritage: it is Europe’s cultural and historical heritage and we’re in a race against time to save it.”

Facebook Twitter Pinterest Natasha Kaplinsky. Photograph: Dave Benett/Getty Images

One of the first buildings in line for restoration is the Great Synagogue in Slonim, Belarus, built in the 1640s. Before the second world war, 17,000 Jews lived in Slonim, more than two-thirds of the local population. An estimated 200 survived.

The synagogue, a baroque building overlooking the marketplace, was used as a warehouse after the war but has been abandoned for 18 years. It has been vandalised and is in danger of collapse, but some of the interior paintings and carvings are intact.

Among those rounded up and killed in Slonim were Kaplinksy’s relatives. The newsreader discovered her Jewish family history when she travelled to the city for the television series Who Do You Think You Are?

“It was devastating to find out that a large number of my family were killed by the Nazis,” she told the Observer. “One key moment [in the Slonim trip] was going to the synagogue where most of my family used to worship before being rounded up and burned alive.”

The synagogue is a “majestic building, absolutely stunning. You can see its history on its walls, but it is falling apart. I was horrified to find swastikas painted on the outside walls.”

After the programme was made, 27 Kaplinsky family members from all over the world met in Belarus to learn more about their history. “We ended up in the synagogue,” Kaplinsky said. “It was hugely symbolic that the building that tore our family apart brought us back together. It was a very special moment.”

There were lessons to be learned from the past, she added. “When you look around the world you can see the devastation caused by prejudice and hatred. We need to educate future generations and remind them of history.”

Discussions are now under way to restore the Slonim synagogue as a Jewish museum, educational and cultural centre, and a place of worship.

In Merthyr Tydfil, the proposal to restore the Old Synagogue as a Jewish museum of Wales and cultural centre is supported by the city council and local politicians.

Gerald Jones, the Labour MP for Merthyr Tydfil and Rhymney, said the restoration plan “would see this building once again playing a part in the life of our community”. The foundation is seeking funding from partners including the Heritage Lottery Fund in the UK. It is also hoping for donations from people with family connections to synagogues.