The El Ghriba Synagogue on Djerba Island may be the oldest Synagogue in the world depending on who you believe. The original buildings on this site were built in 586 BC or about 2,600 years ago, in which case it definitely is Or maybe it was built in 80 AD or about 1960 year ago, in which case it's not.
Either way this is a very old, very important synagogue, and if you haven't guessed it, these buildings are 2000 odd years old - it was rebuilt in the 19th century.
But again it's another one of those things you find in the weirdly underrated Tunisia - if you like history then this place is a goldmine. Roman ruins, Cathegian ruins, very important Muslim mosques, important Jewish Temples and then all of the other stuff, seriously go to Tunisia, now.
