Hundreds of pigeon towers or dovecotes, dating largely to the Safavid reign, dot the fields in the vicinity of Isfahan. Distinct examples of secular architecture in Iran, these structures played an important role, much alike the subterranean canal system (qanats), in sustaining the hinterland that made possible an urban center at Isfahan. The turrets built with the purpose of collecting pigeon dung were a significant source of local revenue and were frequently decorated with white plaster and crenellations.
These cylindrical towers constructed of brick, gypsum, and lime plaster would range from 15 to 25 meters in diameter to often imposing heights of 20 meters or more. Topped with domes with crevices to allow access to honeycombed interiors, each pigeon tower could accommodate thousands of the Persian wild pigeon that could be harvested annually for dung to manure fields and soften leather in Isfahan's famed tanneries. Agriculture in the fertile but nitrogen lacking Isfahan plains was largely supported in this manner, and the legendary melons grown in the region were particularly dependent on this fertilizer. These structures have been deteriorating with little maintenance ever since they were rendered functionally obsolete with modern use of chemical fertilizers and tanning chemicals. There has been a significant drop in pigeon tower numbers from the thousands reported in seventeenth century accounts of Safavid Isfahan by French traveler Chardin, to the present day count of approximately a remaining hundred in the entire province.
Hutt, Anthony and Leonard Harrow. Islam Architecture: Iran I. London: Scorpion Publishers, 1978. 171.