For centuries Esfahan relied on pigeons to supply guano as fertiliser for the city’s famous fields of watermelons. The guano was collected in almost 3000 squat, circular pigeon towers, each able to house about 14,000 birds. Today they are unused, made redundant by chemical fertiliser, but more than 700 of the mud-brick towers remain in the city’s environs. The best place to see them is along the Zayandeh River south of the Ateshkadeh-ye Esfahan (Fire Temple).