Zanzibar is an island off the coast of Tanzania with white sand, clear shallows and triangular dhow sails, and almost everything that made it came across that water. Even the spice. Cloves are not native: an Omani sultan had the trees carried from Indonesia and planted in the 1810s, and within decades this one island supplied four-fifths of the world. The unopened buds were worth enough to be called black gold. They are still taken by hand: pickers climb the trees, gather the buds before they open, and spread them in the sun until they darken and curl. On a spice farm a guide snaps twigs, roots and pods for you to smell: clove, nutmeg, cinnamon, cardamom and vanilla growing side by side.
Stone Town is the old capital, a maze of coral-stone alleys too narrow for cars. An afternoon there pulls you off whatever route you planned, past heavy brass-studded doors and the sultans' palaces, and puts you out at the seafront. The coast does something else twice a day. On the east side the tide draws back for hundreds of metres and leaves a plain of wet sand, tidal pools and stranded boats, with women out on it working the staked rows of the seaweed farms. That crop reached Zanzibar only in the late 1980s, and nine in ten of the farmers are women. Boatmen run out to reefs where the water goes from pale green to deep blue over the coral. Inland, a boardwalk into Jozani Forest finds the Zanzibar red colobus, a russet, tuft-headed monkey that lives nowhere else. In the late afternoon a dhow takes you out over the shallows under one triangular sail, no engine, just the creak of timber and the water going past. At Nungwi on the northern tip they are still making them, shaping ribs and planks by hand with simple tools on the open sand.