The Stone Town is the product of at least three centuries of continuous settlement, but it was only from 1830 that Zanzibar took on a wholly urban character and that stone buildings were built in significant numbers. Until that time, the majority of houses were made of mud and wattle, and roofed with palm leaf thatch. Very few large-scale structures could be distinguished, besides the Fort and a few small mosques.
At the beginning of the nineteenth century, the town occupied only the north-eastern portion of the peninsula, extending from Shangani Point toward the creek's narrowest crossing at Darajani. After the Omani Sultan's permanent move to the island in 1832, the Stone Town quickly expanded during the middle of the century, filling in the areas of upper Sokomuhogo, Forodhani, Kajificheni, and Kiponda. The Omanis erected palaces and residences along and behind the sea front, and tradesmen from the Indian sub-continent built up the bazaar streets with shop-front houses, and sea-faring merchants built houses, sheds, and warehouses near the waterfront. After 1850, stone buildings spread further and began to extend north into Malindi, south into the lower portion of Sokomuhogo, and east to Mkunazini, areas which up to this time had been mostly occupied by mud buildings. As contact with western trading markets increased, particularly once the Suez Canal opened in 1869, and later with the establishment of the British administration in 1890, specialised structures - larger civic buildings in particular - began to appear. The building up of the Stone Town was more or less completed and the present limits defined by the first quarter of the twentieth century: the new port area to the north had been reclaimed, the area south of Shangani built up, the European garden suburb of Vuga laid out, and the programme to fill the creek bordering the peninsula to the east gradually put into effect.
Thus, within the relatively short span of one hundred and fifty years, the confluence of several distinct cultures and the island's intense cosmopolitan development produced the rich and diverse architectural heritage we see today. In some cases, the diversity of the original imports is still evident in different sections of town; in others, the borrowing and adaptation of forms from other contexts produced a cross-fertilisation of different building traditions. In yet other cases, buildings were gradually transformed over time as newcomers adapted existing structures to their tastes and preferences, thus determining a further hybridisation of forms. This variety produced the diverse spaces and surprising contrasts of the Zanzibar townscape, where pedestrians move from the imposing row of sea front structures to the crowded and lively atmosphere of the Indian bazaars, and the quiet, intimate spaces of the narrower residential streets. Thus, although the different forms and building types and their origins - African, Arab, Indian, or European - can be recognised, it is the synthesis of these cultures and influences that creates Zanzibar's unique urban and architectural environment.