One of the more unusual facts I learnt during my Danube waterways cruise was told to me in Budapest. As we passed the University, our guide, Cathy, pointed out that Ernõ Rubik, who invented the Rubik's Cube in 1974 originally to teach three-dimensional applications to his architectural students, is an occasional lecturer there. Ernõ was born in 1944 while his Jewish parents were in hiding from the Nazis.
The Danube, Europe's second longest river, is an international waterway that meanders some 2,850 km (1771 miles) from Germany's Black Forest Mountains passing through four Central and Eastern European capitals before settling into the Black Sea.
We were on a Jewish Heritage river cruise arranged by Voyana Cruises and Budapest was the first stop followed by Bratislava, Vienna, Durnsten, Melk, Linz and ended at Vilhofen in Germany.
As rivers have always been the ancient highways of large areas of population, there was no problem (with the exception of Vienna) anchoring right alongside the historical centre.
It turned out to be a fun, hassle-free way of sightseeing without the need for packing or unpacking; of enjoying the different treats of each destination, minus the hassle of finding somewhere to stay.
The boats are sleek and slender, to accommodate the river's small ports, low bridges and sometimes quite shallow water. Accommodation is spacious and well appointed with a small but comfortable en-suite bathroom. The food was top class, and seemed to be on offer virtually all day, with buffet-style service at breakfast and lunch with loads of choice, and table service at dinner. It was easy to see why river cruising is so popular.
At each port we were given headphones and transmitters so we could hear our guides, even if they went out of sight. It meant we could linger for a while knowing it was possible to catch up with the rest of the party and avoid getting lost.
Our Jewish Heritage Tour of Buda and Pest sprawled out over both sides of the Danube and started in the magnificent Dohany Synagogue, one of the city's top 10 tourist sites. It is the largest in Europe and is now tastefully restored, thanks to wealthy donors, including Estée Lauder and the late Bernard Schwartz, more commonly known as Tony Curtis. The latter also chaired a foundation for the restoration of all the synagogues and Jewish cemeteries in Hungary.
There is a wow factor in entering Dohany, with its attractive interior and space to hold 3,000 people. Curiously outside, the onion-shaped gilded spheres resembles a mosque.
During his explanation about the architecture, our guide also told us the sad story of Jewish Budapest and how every third person in Auschwitz was Hungarian. Next door, the
Jewish Museum is built on the site of the house where Theodore Herzl, founder of political Zionism, was born. On the Pest side is the poignant "Shoes on the Danube Promenade" memorial. It was created by Gyula Pauer and Can Togay in 2005 to honour the victims of the fascist Arrow Cross.
During World War II these militiamen shot their Jewish victims into the river, sparing themselves the hard work of burials. Before the shooting, the order was given to take off all footwear, as shoes were valuable belongings at that time. The iron sculpture of 60 pairs of 1940's shoes forms a 40-metre row and are a powerful reminder of that terrible time.
Bratislava, the capital of Slovakia, is compact and we sauntered around the city quite quickly. Cheeky statues add a touch of Hollywood-style gaiety and we could marvel at the wonderful 13th century castle in the distance.
A Holocaust memorial marks the spot where a synagogue was razed to make way for a road bridge.
Finally, a coach took us to the grave of Chatam Sofer who made the city's yeshiva, world famous. His monument is on the site of the original Jewish cemetery destroyed in 1942. Sadly, we did not have time to visit the Museum of Jewish Culture. Forty miles away in Vienna, Austria's capital, The Hologram exhibition in the Jewish Museum portrays important points of Jewish history and at the same time emphasises the ethereal nature of its existence.
At the northern end of Judenplatz is the memorial known as the Nameless Library designed by British sculptor Rachel Whiteread. It is a concrete 3.8m high block and draws upon the frequent description of Jews as "People of the Book". All the identical volumes are inside out with the pages showing and the titles turned inward. Like those who lost their lives, the contents cannot be accessed. There is no way to enter this library because the doors have no hinges or handles. Engraved around the base are the names of the 41 extermination camps where Viennese Jews were sent to their deaths.
The more conventional beauty of Durnstein lies in its baroque tower in the Wachau district of Austria while Melk is a sleepy village with a large abbey dating back to 976 when it was Leopold I's castle.
In Austria's second city, Linz, there was time to visit the Alter Markt and view the site of the Old Synagogue before driving to the Jewish Cemetery. The tour ended at the New Synagogue.
Jewish families lived in the old city from the second half of the 13th century, and until 1420, there was a Jewish quarter, as opposed to an isolated ghetto. Then came the years of persecution when Jews could choose between being Christened or suffer death by fire.
The cruise ended with a chance to see the old town of Vilshofen with its imposing double-towers of the Benedictine abbey, Schweiklberg, which dominates the scenery. Then it was on to the beautiful 2,000 year-old city of Passau, often referred to as Venice on the Danube due to its unique location.