The oldest Jewish congregation in South Africa, founded in 1841, is Gardens Shul (formerly Cape Town Hebrew Congregation). It is considered the "Mother Synagogue" of South Africa. It includes two buildings, an 1863 synagogue and a 1905 synagogue. (The originally 1849 building is gone.)
A guide told us that this orthodox synagogue seats 1,100. Since there are only 800 Orthodox Jews in Cape Town, it's probably never hard to find a seat.
I loved the stained glass windows, not something I usually associate with Judaism:
Close-up of two of the panes: