The earliest visitors to Zanzibar were Arab traders who are said to have arrived in the 8th century. The earliest building that remains on Zanzibar is the mosque at Kizimkazi, which dates from 1107, and is a present-day tourist attraction. For centuries the Arabs sailed with the monsoon winds from Oman to trade primarily in ivory, slaves and spices. The two main islands, Unguja (normally known as Zanzibar Island) and Pemba, provided an ideal base for the Omani Arabs, being relatively small, and therefore fairly easy to defend. Indeed, in 1832, Sultan Seyyid Said, of the Busaid dynasty that had emerged in Oman, moved his Sultanate from Muscat to Zanzibar, perhaps making it easier to protect, where he and his descendants ruled for over 130 years. Most of the wealth lay in the hands of the Arab community, who were the main landowners at that time. They kept themselves to themselves, and generally did not intermarry with the Africans.