Among the earliest accounts of East Africa, the works of Al-Masudi describe early Islamic trade routes, and how the coast and islands were frequently visited by Muslims including Persian and Arab merchants and sailors in search of coral, ambergris, ivory, tortoiseshell, gold and slaves. They also brought Islam to the people of the Zanj including the Comoros. As the importance of the Comoros grew along the East African coast, both small and large mosques were constructed. The Comoros are part of the Swahili cultural and economic complex and the islands became a major hub of trade and an important location in a network of trading towns that included Kilwa, in present-day Tanzania, Sofala (an outlet for Zimbabwean gold), in Mozambique, and Mombasa in Kenya.