Christ Church is the seat of the Anglican Diocese of Zanzibar and the single most important historical site in Stone Town. The slave market on this spot was the largest in East Africa, where captives were brought from the interior and sold on for the Arab and Indian Ocean trade. The cathedral was deliberately built over it in the 1870s as a monument and rebuke.
The most affecting part of the visit is below ground: two stone cellars where captives were held in the days before sale, the ceilings too low to stand in, the air still and heavy. In the small garden outside the cathedral is a sunken sculpture by Clara Sornas of five figures chained at the neck by an original iron collar from the trade. The combined ticket includes the cellars and the small museum next door. Allow an hour and a half.