It happened in 1421 in Vienna. It had happened in 1182 in Paris, in 1290 in England and in 1348 in Strasbourg, then part of Germany. The Jews were forcibly converted, killed or expelled and their synagogue destroyed. In some cases they returned within a few years, but in England and Vienna not for hundreds of years. In Vienna the poorer Jews who refused to convert to Christianity were deprived of their meager property and foodstuff and set on rudderless boats on the Danube which floated them into Hungary, where it seems they managed to survive. But Vienna did not see them again for 200 years.
What happened in 1421? In Vienna, all Jews were under the jurisdiction and protection of Duke Albrecht V. Although the pope wanted him to expel the Jews, the Duke didn't want to lose face. However, a concocted libel that Jews had descrated the host took the matter out of his hands. At the request of the church, on May 23, 1420, the Duke ordered the Jews to forcibly convert. Those who had not converted, escaped or sent off in boats were burned on March 12, 1421, and the synagogue destroyed.
Fast forward to 1995, a memorial is planned for the victims of the Holocaust by Vienna in the Judenplatz - the medieval Jewry center. An archaeological team was sent to see if there were any remains. In one word, the find was sensational.
Less than three meters below ground level, the experts came across the stump walls and foundations of the medieval synagogue that had been destroyed in 1421. Its ground plan was clear and the archaeologists could discern that it had stood over a period of 200 years, in three distinct phases. Nearby they went down even further and found that the whole area had been used to build wooden barracks in the second century for the Roman soldiers that had occupied the area, then called Vindobona.The earliest synagogue was a rectangular room, dated to 1236 by an Austrian penny found on the floor. The ark wall faced southeast towards Jerusalem, with an entrance to the north and a women's room on the south with openings into the main room.
To the credit of the city fathers, their experts were allowed to work for three years to make a meticulous record of the three phases of the synagogue and to preserve its remains within an underground annex to what was to become the Jewish Museum of medieval Vienna. What did this medieval synagogue look like? As usual with archaeological digs, a certain amount of imagination is required, but here there were a large number of clues. The whole history of the terrible events of 1420/1 had been recorded in a Hebrew document called the Gezera of Vienna, which aimed to warn other cities of what the future might hold for them.
The community grew; the synagogue doubled with added columns. A unique feature was a hexagonal bima, hung with oil lamps whose remains were found. In 1350, the hall was again extended, the ark placed further east, side rooms added and the women's annex enlarged.
Also found were:
"... a fine wooden comb (of the kind still used today to check for lice eggs), a large drinking beaker, the remains of a small toy horse and rider and a metal stylus, as used for writing on wax. The handle was in the shape of a young boy, and possibly these finds indicate the use of the rooms for a Hebrew school for youngsters. Another find was a medieval key, perhaps even the key used by the shamash (beadle) to lock up the synagogue."In 1624, Emperor Ferdinand II allowed the Jews to return and settle in Leopoldstadt; by 1670, there were 137 dwellings and some 500 Jewish families.
In 1825, another synagogue was built in the main town, the first erected after the medieval one. Built behind a residential facade, it escaped the 1938 Kristallnacht, although it was later ransacked. Now restored, it is called the Stadttempel. The underground medieval synagogue is today a museum, displaying historical finds.
There is much more; read the complete story at the link above.