In the 1690s Saif bin Sultan, the imam of Oman, pressed down the east African coast. A major obstacle was Fort Jesus, housing the garrison of a Portuguese settlement at Mombasa. After a two-year siege, it fell to Saif in 1698. Thereafter the Omanis easily ejected the Portuguese from Zanzibar and from all other coastal regions north of Mozambique. Zanzibar was a valuable property as the main slave market of the east African coast, and became an increasingly important part of the Omani empire, a fact reflected by the decision of the greatest 19th century sultan of Oman, Sa'id ibn Sultan, to make it from 1837 his main place of residence. Sa'id built impressive palaces and gardens in Zanzibar. He improved the island's economy by introducing cloves, sugar and indigo though at the same time he accepted a financial loss in cooperating with British attempts to end Zanzibar's slave trade. The link with Oman was broken after his death in 1856. Rivalry between his two sons was resolved, with the help of forceful British diplomacy, when one of them, Majid, succeeded to Zanzibar and to the many regions claimed by the family on the east African coast. The other, Thuwaini, inherited Muscat and Oman.