The major buildings date from the 18th and 19th centuries and include monuments like the Old Fort, built on the site of an earlier Portuguese church; the House of Wonder, a large ceremonial palace built by Sultan Barghash; the Old Dispensary; St. Joseph's Roman Catholic Cathedral; and Christ Church Anglican Cathedral, marking the work of David Livingston in abolishing the slave trade. The Stone Town of Zanzibar is a fine example of the Swahili coastal trading towns of East Africa. It maintains its urban fabric and townscape virtually intact and contains many fine buildings that reflect its unique culture.