Pigeon towers were often over six stories high and 45 to 75 feet in diameter, these towering structures were filled with a honeycomb of small roosts for the pigeons. These towers were constructed as impenetrable fortresses that could shelter the pigeons from predators. The towers would open once a year to collect their droppings for harvesting the crops.
Probably, it wasn’t a very pleasant experience for the people to collect the pigeon droppings which accumulated for a whole year. But a bumper harvest at the end of the season was the reward, they care about. Today, due to the use of artificial fertilizer the role of these towers has declined. Most of these towers are in ruins but government of Iran has started to renovate them and one in Isfahan is an example of that drive.