The two slim spires of St. Joseph's rise unexpectedly out of the alleys and are one of the navigational landmarks of Stone Town from the rooftops. The cathedral was built between 1893 and 1898 by French missionaries to a design by the architect of the Marseille cathedral, in pale stone shipped from Marseille itself; the interior is painted with frescoes of saints and East African scenes, and the windows tinted in cobalt blue.
The cathedral is still in active use as the Catholic seat of Zanzibar, with services in Swahili. Casual visitors are welcome between services; donations support the upkeep of the painted ceiling. It sits a short walk from the slave market memorial and pairs naturally with that visit.