What it is
Unguja, the main island, about half an hour's flight from Dar es Salaam. Stone Town is a dense quarter of coral-rag houses, carved doors and alleys you will get lost in. The beaches ring the coast and differ sharply from one side to the other.
Why go
The obvious second half of a safari: reef diving, dhow trips, spice farms, and Jozani Forest with its red colobus. Stone Town deserves a night of its own — the history here is cloves and slaving, and the museums do not soften it.
When to go
June to October and December to February. April and May bring the heaviest rain. The detail that catches people out is the tide: the east coast beaches, Paje and Jambiani, have a huge tidal range and the sea walks out hundreds of metres twice a day, which is why kitesurfers go there. The north, Nungwi and Kendwa, swims at any tide. Zanzibar is Muslim-majority: cover shoulders and knees in town and villages, and expect shorter hours and quieter days during Ramadan.
Most people stay 4-5 nights.