The Ancient Synagogue of Barcelona was built in the sixth century and is the oldest saving synagogue in Spain and one of five medieval synagogues in the world. It was built underground because because no house of worship was allowed to be taller than the smallest Catholic church. Of course then came The Spanish Inquisition 1391 and the Jewish quarter was sacked and over 300 were killed. Jews were forced to turnover all their possessions to the King and permitted to leave the country. The alternative was death of conversion to Catholicism. The Nazi’s didn’t invent this stuff they were just more efficient at it.
Today the synagogue is a museum. Barcelona has two working synagogues and a pollution of around 15,000 jewish people with about 45,000 in Spain. Of course like jewish people all over the world they face anti semitism but in Spain like the United States they are now free to practice their faith.