Qanbalu occupied a prominent place in descriptions of the early medieval sea of Zanj. Voyages from Oman and Siraf crossed the Indian Ocean to reach the island, which was treated as a principal destination for maritime traffic. The distances recorded by contemporary writers also place Qanbalu within a wider commercial system extending southward toward Sofala, Waq-Waq, and the lower Mozambique coast.

Al-Mas'udi described Qanbalu as having a partly Muslim population and a ruling family, while its Muslims spoke the language of the Zanj. He reported that Muslims had conquered the Zanj of the island around the transition from the Umayyad to the Abbasid dynasty, approximately AD 750. This episode is presented as the only evidence in the chapter for immigration to the East African coast at such an early date.

Buzurg described a town surrounded by a strong wall and associated with an estuary. The island is most probably identified with Pemba, especially through the evidence of Yaqut, who mentioned two cities whose names may correspond to Mkumbuu and Mtambwe Kuu. Because the chapter emphasizes the limits of the evidence and the absence of tenth-century remains at the proposed site, Qanbalu’s precise location remains provisional.