Put all ingredients except pears in a large saucepan. Bring mixture to a boil, stirring until the sugar is dissolved. Reduce heat and simmer, uncovered, 15 minutes.
Peel pears, leaving stems intact, and gently slide them into poaching liquid. Simmer, uncovered, gently turning from time to time, until tender, 20-30 minutes depending on ripeness.
With a slotted spoon carefully transfer pears to a bowl.
Continue to boil the poaching liquid until reduced to about 1½ cups, about 10 minutes. Discard allspice, ginger, cinnamon and zest.
Serve pears at room temperature with a bit of syrup.